The 3 new dslrs for 2012:
1) 7d mk II entry level FF, of which we have heard much
2) A pre-announcement of a higher-MP FF in the fall, availability early 2013.
3) The 70D
We haven't heard much about the 70D. There was a report on NL that it would be 22 MP. Most folks seem to think it will be the same-O 18 mp.
Here's my speculative pitch for a new sensor with new technology and a departure in better performance making its debut on the 70D:
1) The current 18MP sensor was introduced with the 7D, then the top of the line aps-c dslr. The 70D will be the new top of the line APS-C dslr, so introduction of a new sensor here has precedent.
2) With the new FF drawing attention, the flagship APS-C dslr could use something more to differentiate it.
3) Introduction of a new sensor with the 70D would provide an upgrade path for the t5i next year. Percolating the new technology up to ff would provide an upgrade technology for a 5D mkIV and 7D mkIII later.
4) A sensor designed from the ground up with PDAF in mind could provide better video af performance.
5) Introduction of new technology with an XXD has precedent; consider gapless microlenses -- introduced with (I think) the 40D, but not on a FF until the 1D-X, if memory serves.
6) Competition with Nikon and Sony. Canon sensor design can not stay stagnant forever. A step forward has to come sooner or later -- the 70D seems like a good place to start.
7) The quietness of 70D rumors -- the very fact that we haven't seen anything solid on the 70D suggests a tight lid on information, which could mean a desire to keep a new sensor with improved technology under wraps...
and ... reason number 8 ...
... wishful thinking on my part.