Since the T2i and T3i both use the same sensor, other than a few gadgets (tilty-swivelly-screen and 3x movie crop mode in 1080p for the t3i instead of 7x in 480p for the t2i), their performance is basically identical. Their price, however, is sometimes so close that it might be worth going for the t3i (if it's like 50$ more).
The T4i is rumored to be announced in June, with yet another 18mp sensor (no one knows if it's a new 18mp sensor, or the old one), 9 cross-point AF points, which could be interesting, touchscreen LCD, and continuous AF in live mode and movie mode.
I'm not too convinced at a first generation LCD touchscreen, usually best to wait a generation or two on those things before manufacturers actually find some good use for it. The rest seems interesting, though.
Cameras: Canon EOS 6D, Canon EOS Rebel T3i, Canon EOS Rebel T2i, Canon S90
Lenses: Tamron: SP 24-70mm F/2.8 Di VC USD, SP 70-300mm F/4-5.6 Di VC USD, Rokinon: 8mm Fisheye cine, Canon: EF-S 18-55mm f/3.5-5.6 IS Lens, 75-300mm f/4.0-5.6 III, and EF 50mm f/1.8 II
Retired camera: Fujifilm Finepix s700