If Canon do release the 70D with same-ish sensor tech then it will pretty much be a disaster. 3 1/2 years without improvement in that area would be a very poor showing. Fluffing around with entry-level / rebel series cameras is possibly excusable, but with the more enthusiast models like the XXD series it would leave a sour taste.
It still could be an ok camera in other respects. And one reason Canon are less vulnerable on this point is that Nikon have their own set of issues (quality control, poor customer service, etc). Just read Thom Hogan.
Mind you, I still think Canon are in a strong position in the DSLR world due to the supreme quality of their lenses, esp. in areas like telephoto, wide-angle TS, macro and standard zoom. Bodies can be refreshed in 2 or 3 years, but revamping a lens portfolio might take closer to a decade. By far the most serious issue Canon have, as someone else pointed out, is the fact that they missed the boat on the mirrorless market.