Nikon Rumors is reporting that Nikon could release four new DSLRs before the end of the year. (Sound familiar?)
Likely candidates are a D400 (Equivalent to the 7DII); the D600 (Low-Cost Full Frame); the equivalent to the 60D/70D and an entry-level Rebel equivalent.
So, that would seem to make the four Canon DSLRs before the end of the year plausible.
At least three of the rumored Nikon DSLRS are directly equivalent to existing or rumored Canon products (60D, 7D and mythical full frame entry level) I think Canon might be done with Rebels for the year, so it's possible that a fourth camera could be a 5DHD (High Definition).
Of course, I was most heartened by the published D600 specifications and rumor that it could be released around Photokina. I don't see Canon allowing Nikon to have the flagship APS-C market to itself, so if the D600 materializes, I expect the 7DII to follow shortly thereafter.