Now that we have the EOS-M here is my thoughts on the future of Canon's APS-C line.
The XXXXD line (T3) will be replaced by the EOS-M. (Logical based on the pricing and compatibility with EF lenses)
The XXXD line will take on the features found in the XXD line. (Logical based on the features found on the new Rebel, it's closer to a merge of a 7D and 60D in a smaller body)
Very possible merger of the XXD line and XD line into the 7D mark II. The 70D (if there is one) will not replace or be better than the 7D replacement. The 7D has been and will remain the flagship APS-C camera for Canon. (The 7D is one of the most popular cameras Canon has ever made, they will continue with the namesake for it's replacement)
The replacement of the 7D will not be FF nor APS-H as the marketing for the 7D has been towards EF-s users. Too many current 7D owners own/use EF-s lenses. (I am one) It would not make for a good marketing shift for Canon to change the body into a different crop of sensor from the APS-C. This is about Canon making money and the smartest choices to convince users to upgrade. If Canon is going to introduce another FF body or "bring back" the APS-H, they will simply call it something other than the 7DX (X being whatever)
If there is a 70D (and based on the August release of the version 2 firmware update for the 7D) it will push the 7D2 into 2013 or possibly 2014. I don't see that happening. There would be little reason for Canon to release such an extensive firmware update IF they were going to announce the 70D anytime soon. The 70D would have to exceed the current 7D in features and speed. (And the 70D will not be FF nor APS-H for the same reason, current XXD users who own/use EF-s lenses) My opinion is that they are trying to keep current 7D users happy while they develop a replacement for the 7D later this year or the beginning of 2013.
I think Canon is shifting the playing field from APS-C bodies to more FF bodies. The rumors of an "entry-level" FF is what makes this future interesting. I can't see Canon having too many camera bodies directly competing with each other. From what I have seen in the past, they like to spread out the choices. Canon taking away (merging) the XXD line will slim out the crop sensor field and make room for more FF cameras.