Maybe we aren't hearing much about the T4i because there isn't one on the horizon?
I'm trying to think what is missing from the current model that would likely be added. How has Canon lost the "edge" against the competition? I admit I don't study camera models that closely, but in looking at the T3i, I'm trying to figure out what they should add to it.
I'm starting to wonder if this isn't the real reason, I think it would be great in marketing terms for them to release the 650D this year: "25 years ago Canon revolutionized photography with the EOS 650, this year they do it again with the 650D" (my speculation on marketing phrase, with no relation to reality) however, I don't really know what they would have to offer to back up a statement like that... Video auto-focus? a slightly improved sensor? in-body IS? face recognition? I doubt any of those would really be enough since either the competition or other models have those features.
That being said I've seen a 24MP rumor but that's about it. Part of me wants them to go ahead and release a new model just to get it out and over with so they can focus on the 7D2 and 70D, but I doubt they'd do anything too drastic since it could impact 60D and 7D sales by making some wait for their replacements for the higher models to get the new features (assuming they wouldn't "downgrade" just for those features).
In my ideal world they'd announce the 5DII and 7D replacements this month or next and then release the 70D and/or 650D later in the year after those models have actually hit the market and the people in those markets at least have their orders placed. It's an interesting idea that they could do the 650 and have features "trickle up" as they test and prove the newer technologies but I am not sure it would bode as well for sales as if they "trickled down".