IMHO Canon should follow similar strategy as Apple (created by S. Jobs) - to get rid of many models in DSLR area and produce only few and apply the top technology.
Also, i think that application of APS-C sensors can not be justified in 2013 as they initially were created due to significant costs of FF sensors. During few years sensor production technology had to become much cheaper. Also, Canon is not making any efforts in distinguishing themselves in the current market. Many consumers are not able to change firm as they already invested in expensive lenses. However, if the same trend will happen for few more years many people might switch to other manufacturers. Now it seems that Canon is sleeping and tries to follow Nikon.
I can not understand why Canon is not mowing to Medium Format cameras? Also, it is very obvious that in mirrorless camera area they are off-competition. It seems that they strategy guys are too old and not able even to follow market trends (from Canon I would expect to be market maker). Currently they are trying to squeeze all possible money from loyal customers and thinking how NOT to produce good camera in order to protect big line of camers. If they put FF sensor, they cripple autofocus, produce good camera 1Dx C however as for it too significant premium compared to almost the same camera 1Dx.
oh, i forgot that strange P&S camera, which they recently introduced. It seems that they do not understand words "customer expectations" (where is Canon 7D Mark II and etc.). Few more years and people will talk about Sony, Tamron, Sigma.... when Canon guys will try to catch up.
Medium format would require an entirely new array of lenses. Also, worse still, an entirely new array of techniques.
APS-C has piles of applications. APS-C and FF are two different tools for two different purposes. APS-C is very valid.
I can see the need for APS-C SLR's diminishing in the future. The crop sensor line up is starting to get eaten into at both ends - cheaper FF SLR's are being introduced, and we'll no doubt see even cheaper FF bodies introduced in the future - and the cheaper end of crop SLR's has mirrorless cameras to compete with, including Canon's own EOS M.
For the first two years of the 7D's life, there were no FF cameras in Canon's line up that could really be seen as an alternative for sports or wildlife - the 1Ds III was much more expensive and was only 5fps, the 5D II had under 4fps with much worse AF, leaving just the 1.3x crop 1D IV. Now we have the 1D X and 5D III - the 1D X is better in every single way except cost, and the 5D III is cheaper, has a faster frame rate and has better AF than the 1Ds III, so it is a viable upgrade for 7D users.
When FF bodies can be made for comparable prices to today's rebels (not impossible - when the sensor becomes as cheap to make as today's APS-C sensors, just package it in a plastic body with a pentamirror), the only need anyone would have for a crop body SLR and not a crop body mirrorless is to get a small camera with a real OVF. That can be covered with just two models - a high end crop camera for birders who only want to carry around a 500/4 instead of an 800/5.6, and something for people that don't want to lug around a big DSLR, but they still want an optical viewfinder.
Having said that, birders can get very good results cropping with FF, or simply throw on a 1.4x TC (or use a 2x instead of a 1.4x). And for the people that want a small normal zoom camera with an OVF, the body could be made very light with plastic construction and a pentamirror, and there's no reason why they couldn't release a lens much like the old 28-90 lens - it weighed in at just 190g - 10g less than the EF-S 18-55.
So, why carry on with crop SLR's at all if full frame sensors drop in price sufficiently? The only real place where it makes sense is mirrorless cameras, and there's still an argument for FF there.