I really do NOT anticipate Canon introducing much more this year, except for the 1Ds Mark IV. Canon has a pretty complete lineup right now, and is doing well in multiple segments. Their 7D is doing very well, and has a solid place in its market segment. The 5D Mark II is doing well,and has an enviable reputation and is doing well in the $2,400 segment. The T2i has good video, high MP statistics, and decent price. The 50D still wins its category MP-wise, which is enough to keep it alive despite mediocre sales. The low-end Rebel market is still doing okay. Canon seems to be doing quite well across a broad range of prices. They have a couple of gaps, which Nikon fills quite well, so there's really not much pressing "need" for Canon to try and introduce cameras that would cut in to the sales numbers for their 1-series cameras. For example, Canon has no answer to the Nikon D700,and if they were to try and move into that category, a new entry could seriously cut in to the 1D Mark IV's sales and its high profit margin, so I think Canon will continue with the 5D-II as a "good enough" body with a good sensor and video, at the $2,399 price point. The 7D is so,so new and is selling well,and is a lot higher-spec'd than the 50D, and it's fulfilling a need at a price that keeps it separated from the 1D Mark IV, but allows buyers to buy lenses with the price difference between a 1D Mark IV and a 7D body.
Like Big Mike said, you could look at Canon's past introductions as a sort-of guide to the future; in looking back, I see Canon as just having made introductions that will carry them through another year, or slightly more. I really think the 5D-II is going to be "it" for a while longer...I do not see Canon moving to offer a more-robust body in the mid-priced FF segment...the "real money" is made at the consumer and mid-level body sales points, where huge unit sales really add up,and new customers join the system.