Price gouging or dragging their feet, that's the Canon way. This will be price gouging because there is no competetive reason to update their lenses. Prepare for a $9,000 + 200mm f/2.0 IS II. Lighter, with better coatings etc.
Maybe not a competitive reason...but a technological one for sure. Older lenses are not necessarily capable of resolving enough detail to support higher density sensors. That fact is often clearly demonstrated in the MTFs of older canon lenses that have just been replaced (like the 24-70/2.
...sometimes the differences are very significant, and often HUGE in the corners. Canon has stuck with an 18mp APS-C sensor for a long time for a reason...it is pushing the limits of what their current lenses are capable of (particularly in the corners, and improved corner performance is a common theme in all of Canon's recent lens releases), and going to smaller pixels will reveal more "softness" (that is really a misnomer, a higher resolution sensor will still do better with current lenses...but its a perception thing...people see "soft" and plain and simply don't like it.)
I would say Canon is updating the bulk of their L-series line of lenses for TECHNOLOGICAL reasons. It's been a decade or more on quite a number of their L-series lenses, and at least that long since any significant improvements in optics and multicoating. Canon only recently (relatively speaking) developed SWC, or Subwavelength Coating, a nano-tech coating that reduces the TOTAL transmission loss in a lens from several percent at least to less than 1% at most. That significantly improves microcontrast in all situations and reduces flare considerably in the worst of situations. They have started using multiple fluorite lens elements as well as aspheric elements in place of multiple UD elements and element groups to reduce weight and produce superior aberration control. Most lens updates going back a number of years were primarily for the addition of IS, with only minor improvements in the optics themselves, so resolution wise, Canon's lenses have been the same for 10-20 years.
Technologically speaking, if Canon really intends to push into the 40, 50, 60mp sensor range or farther on the FF side, and 20-30mp on the APS-C side, refreshing their line of lenses for significantly superior optics is a smart thing to do. This new line of lenses should last for the next decade, maybe two?
These lenses aren't cheap because there is a lot of R&D invested in them. Canon is refreshing the bulk of their lens line, and along the way has designed and patented a lot of new technologies that will likely find their way into new lenses as well. All that R&D costs millions. Personally, I'd rather have Canon be smart and savvy about where they take their DSLR technology, and release lenses that are up to snuff for higher density sensors BEFORE they hit the market...than have them go the Nikon route and have the bulk of their customers complain about insufficient IS or poor optics that prevent taking tack-sharp photos with the likes of the D800, D600, or D3200. Canon has a cohesive, long-term vision for their photographic equipment
...something I wouldn't say the competition does nearly as well (or doesn't do at all...just look at how Nikon has named their DSLR cameras over the last decade to see how addled that corporate brain is...). Brand new lenses cost a lot of money...its a hell of a lot of extremely advanced optical technology (and I'd argue that Canon has the best DSLR optics on the planet right now, with the HIGHEST QUALITY, backed up by the BEST SUPPORT in the industry) that cost a crap-ton of money to design and develop. If you want the best of the best, and want it right now...well, PAY UP! If not...the prices will drop soon enough, once the high demand and backlog have subsided.
I believe you, @Radiating, have Greener Grass syndrome. You look across the fence and see something in those fields of Nikon D800's and think Nikon is doing everything right and Canon is doing everything wrong. You should hop around the net for a while and read various Nikon forums for a while. Those guys bitch so much about their Nikon gear, you'd think they were Canonites in Nikon clothing! There is no greener grass. Nikon has a few cameras with a whopping good sensor, and a COUPLE of their recently released lenses are great (like the 80-400). A LOT of Nikon stuff, however, including the vaunted D800 and D600, have had more than their fair share of problems. The only significant "problem" to hit the 5D III was the light leak issue, and Canon responded quickly. Check out the number of problems the D800 and D600 have and are still having, and read all the forums where Nikon users are STILL complaining about such issues (as well as complaining about the horrible support experiences they have had on a regular and continuing basis with Nikon customer support.)
There is no greener grass, every brand has its problems, its lagging technology, its missteps and glitches, etc. Right now, when it comes to lenses, Canon's new releases are the creme of the crop. They are lighter, better balanced, have the best IS available, support the fastest and most precise AF (especially when paired with a new Canon body that supports new AF drive functionality), offer unparalleled sharpness, and are ready for the future. I'd happily give up a couple stops of low ISO DR for that. A lens can last for a lifetime. Camera bodies come and go. I think Canon will have the best of all worlds...lens, sensor, AF, ISO, everything...soon enough.