It's plausible that the 7D could carry on whilst the 650D & 70D get new higher MPx sensors (22-24 range) - remember the AF is the key selling point with the 7D along with a degree of user compatibility with the 5DII. A leapfrog crop chip (25-28 range) could come 12 months from now for a 7D with a trickle down to a 700D and 80D ! Gawd, did I just blow a whole year of two model ranges away in one sentence ! Point being, the 7D is a pro camera, it isn't sold on the same headlines as the lesser models.
Conversely, could a dual 7D/1Dv be sensible for launch to tie into the 2012 games ? Both are aimed at fast action sports.
There are merits in either marketing strategy, and it depends on the market you are playing in. Car manufacturers, when they launch a new model, often leave the high performance variants until last in the release schedule - for instance, when VW launch a new Gold, the GTI and R models after often delayed.
Canon are probably in a bit more of a pickle with APS-C sensor cameras, as the 7D is not really due for refresh, but expectations in the lower end of the consumer market may force their hand with a higher resolution sensor.
On the full frame side, they could launch the 5FmkIII first in the hope that pros will buy it and then upgrade when the 1DsIV or 1DV is launched, or they could launch the 1DsIV or 1DV first in the hope that pros who migrated to the 5DmkII will go back to a 1D or 1Ds.
Either way, I suspect a lot of people will sit on the fence until the successor to the 5DmkII and 1DsIII have both been launched and the support for them is available in Lightroom/Aperture and friends before making a decision. That will allow them to make a decision that is appropriate to their needs, and get a camera (as has been pointed out before) that fits into their workflow. (There is not much point in having to use DPP to pre-process photos to get them into Lightroom, because lightroom can't support your camera properly.)