Your impression of the 5D release schedule is not accurate. There is a nice chart here (http://en.wikipedia.org/wiki/Canon_EOS_5D) showing the release cycles for all of Canon's DSLR products. As you can see, if they follow the same release cycle they have for the previous 3 iterations of the 5D, we should be seeing a new 5D soon. The 6D and 1D will be coming a bit later, if they follow they release cycles they have been using for the last decade. So, a 5D later this year, and 6D and 1D revisions coming out in the first half of 2015. The 7D is long overdue, and probably the reason for that is the increased importance of video. The 70D likely acted as a stop gap since they would have been aware of the impending video revolution, so the 7D may have been delayed to catch the cusp of that.
Whatever your opinion, if Canon do what they have always been doing, we should see almost all lines undergo a revision in the next 9-12 months.
That chart actually shows almost a 4 year gap between 5D2 and 3. This is basically accurate as the 5D3 was released in the first half of 2012 and the 5D2 was in the middle of 2008. I know this because I owned both from their respective release times. Based on that time line, we won't be seeing a 5D4 until the beginning of 2016. That is not 9-12 months from now. Pretty sure that makes me right, and inevitably, you wrong.
Furthermore, 1-2 years in tech time is pretty huge. The point most of us have been making is that it is not going to happen right now or "soon." Unless you consider "soon" to be 1-2 years from now which would then make it a difference of opinion as to what "soon" actually is.
As I've stated before, I don't think it would necessarily be a stretch to see it in AT LEAST a year which is definitely not "soon" in my book.
Plenty of other outside factors would have to change in order for this to happen (with Canon) in the non-Cinema xD lines.
As others have mentioned, storage is still a major issue. Yes, the necessary cards are already available, but they are nowhere near affordable for the majority of the market which is who will have to be on board before 4k makes it to those lines.
What the chart shows is that they average a three year release cycle for their mid to high end products. Sometimes a bit longer, sometimes a bit shorter, but mostly it is three years. The three year mark for the 5D3 comes up at the end of 2014, which is approximately when rumour has the third DSLR showing up for this year.
What you appear to believe is that Canon will buck their routine upgrade cycle and do nothing because competitors are introducing the next technology, and Canon does not want to impede their commercial success. I disagree with that. I believe that Canon will stick to the formula they have used since their first digital camera was introduced and I believe that they will meet competition by introducing products that can take those competitive products head on. I believe that Canon is in this business to make money, and I do not think that they will see it as being in their best interests to stand aside and watch their competitors take market share while they do nothing. Call me crazy, but doing something like that seems like pretty stupid business practice and I don't believe that Canon are stupid businessmen/women.
SDHC/XC cards currently on the market are quite capable of handling the sorts of storage a 4K camera's compressed file would require. There are 4K cameras being released this year that we already know about that use SDXC cards for storage, so why will this be impossible for Canon to do? The cameras can't do 4K raw, but that is irrelevant since the internal storage is in compressed formats. Uncompressed output from HDMI can be recorded to an external device if you need that, and that technology is already available in current generation cameras. That would not be an impediment to release.
There is no way the 5D III is being replaced this year. Not a chance. It's a SUPERB camera, and the 5D II lasted closer to four years than three. I don't expect to even see CR2 rumors for the 5D IV until next year, and I don't expect it to hit the streets until the end of 2015/early 2016. The 1D X won't be replaced any time soon, either...it's just too good a camera. It would be unwise for Canon to release new models for at least another year and a half (especially considering the 1D X didn't actually hit the streets until the better part of a year after it had been announced.)
There is no hard "schedule" here. Canon has no obligation to release new models on a set schedule. If you want to find a trend out of only three 5D line releases (two time spans), the "trend" is that Canon is increasing the time between releases. It was almost exactly three years between the 5D and 5D III. It was almost three years six months between the 5D II and 5D III. If that "trend" holds true, then we won't be seeing the 5D IV until March 2016 (almost exactly four years since March 2012, when the 5D III actually hit the streets.) That fits exactly in line with what I'd expect, given how good a camera it is. The only improvement I hear people demanding for the 5D III is more DR, but it really just doesn't seem like enough of an upgrade to release the 5D IV. Such an upgrade would have to be more substantial.
Perhaps we get some kind of interim update in 2015...the 5D IIIn....with an improved sensor....maybe.
The comment about the GH4 being the fire that would spur Canon into action and put 4k in all their cameras is what originally spurred the debate. There is no question that 4k is around the corner. How far off that corner is is up for debate...some seem to think were right on top of it, but from a consumer consumption standpoint, it's still a few years off...sometime 2016 at the earliest is when I think people will begin to regularly buy 4k TVs and might start getting 4k computer screens and would then actually be able to utilize the 4k video they are taking with their phones (assuming they ARE taking 4k video...I suspect 1080 and 720 will remain the video choices of consumers for a while yet, due to smaller files, quicker upload times.)
The GH4 is not going to spur Canon into action. That's been the debate in this thread for some time, and I completely agree with John here. Canon just isn't threatened by Panasonic. They aren't even really threatened by Nikon, who is their largest competitor by market share! Canon will do what Canon does on Canon's timetable. For those who don't like that, you might as well pick up a 4k "camera" from some other manufacturer, because Canon won't make a broad move into 4k until they are sure to make a boatload off of the feature.
As far as high end DSLRs go, Canon may bring 4k to the 1D X an 5D III via firmware. Their sensors are high enough resolution, and for standard cinematic frame rates, they have enough bandwidth for compressed 4k. When it comes to RAW 4k, I really do not expect to see that from any lower end Canon DSLR that currently exists, and I suspect it will end up being relegated to Cinema EOS and Magic Lantern. But as others have already mentioned, to handle RAW 4k, you need significantly greater storage throughput, so that is unlikely to happen until the next generation of high end DSLRs. I figure there is a 50/50 chance the 7D II will get it...depends on whether the rumor about it being more video-heavy are true or not.
If you follow what is happening among their camcorders and not just DSLRs, it is quite clear that there was an abrupt change of direction in the first half of 2013. They released the G20, and then a few months later the G30, which was almost the same camera as the HA20/25. The release cycle should have been the G20 in 2013, with advanced features in the HA20/25 in 2013 as well. Then, in 2014 the innards of the HA20/25 would trickle down to the enthusiast consumer in the form of the G30. But instead the G30 came out in 2013, mere months after the G20. That does not make sense, the only reasonable explanation is that their development cycle for 4K was accelerated in response to probable competition from Sony and Panasonic, so the G30 was sent to market early to recover investment (since it was not going to sell when competing against camcorders like the AX100)
You can't just look at DSLRs in isolation, you have to look at in the context of what is happening in the broader video market since that is going to have a big impact on the design and type of DSLRs being released.
You've switched to an entirely different market now. Camcorders ARE VIDEO DEVICES. The expectation for a video device in a video market getting 4k capability is far higher than the expectation for photography devices in a photography market that happen to also have video features to get 4k capabilities. DSLRs are still first and foremost still photography devices. There may be some broader market concerns, but to say that all Canon DSLRs should suddenly get 4k capabilities because Canon's camcorders did? Well, that is applying FAR too much weight to the video capabilities of Canon's photography devices. It's an added bonus, but the very vast majority of DSLR users use their cameras for photography. There are some specific models that have a history of use as low-end cinematography equipment, namely the 5D II and III, but that is kind of a niche use, and the 5D II was somewhat unique in that it brought a FF sensor capable of shooting video with high quality lenses to a market segment that was desperate for such an offering. Today, that isn't so much the case, there is heavy competition in the midrange 2k and 4k cinema market, and prices are becoming more and more reasonable.
As for what a "reasonable" expectation is, it really depends. What did Canon announce when they released the G30? From what I've read, the G20 and G30 are pretty different cameras. The former has a higher resolution sensor, the latter has twice the zoom range on the lens. They definitely don't sound like the same camera to me, so the fact that they both exist in the market at the same time indicates the G30 is not so much a successor as an alternative.