Re Canon FF Strategyhttp://www.northlight-images.co.uk/cameras/Canon_1DS_MkIV.html
Scroll down to the 18th June IIRC from Canon Product Manager
Downscaling the size of the sensor hits the limits of how much you can cram in there far quicker than FF and also gives you less control over depth of field - one of the biggest strengths or weaknesses compact camera sensors (ignoring the APS ones) depending on your POV.
I would be interested to know how much additional cost there is for a single FF sensor family vs maintaining 2 development and production threads for a FF and 1.3. Add in 1.6x and I think the comparison would be even more compelling. You could just roll down each generation from Pro to Prosumer etc, and then just replace the high-end one. Give it 5-6 years and your entry-level dSlR would have the same sensor as the Pro one had with perhaps just some small tweaks.
Also it's not just a size consideration viz a vie materials, you have more / smaller photo-sensors in an APS sensor vs FF just to achieve the same MP, and your R&D on how to squeeze even more "light-reception" into the same area becomes more and more difficult for each generation, until you manage that next leap in technology - be that foveon or something else.
Finally, Canon would be able to drop their EF-S lens development cycle and focus back again on EF.
So for me, if they want to continue the MP race and if they want to shake it up but simplify their lines then reducing the number of sensors and relegating smaller sensors to entry models just seems a good solution. As the efficiency of manufacturing / tech continues, then I would phase out APS all together.
But hey, I don't work for Canon, I just use their kit