Should I wait for T3i or buy T2i now?
If you dont have any urgent assignment to photograph then its a no-brainer to wait & see what the specs of the new camera are.
Ofcourse it wont be as cheap as the T2i/550D.
However, if you compare the 550D & 60D - http://www.dpreview.com/reviews/sidebyside.asp
Only pluses the 60D has over the 550D is the slightly faster frame rate - 3.7fps vs 5.3fps,
The Inbuilt Wireless Flash Transmitter & the Articulating Screen.
The 550D on the other hand has Timelapse Recording which the 60D dosent besides being lighter @ 530g Vs 755g.
And then, there's the $300/- Price Gap between the 2.
Option 2 - Buy the 550D unless you want a bit more speedy shooting & just have to have the Articulating Screen
Option 1 - WAIT for the newer camera to launch, you have more to choose from
The catch is,
550D = ~$700/- at presant
60D = ~$1000/- at presant
600D/T3i or whatever its gonna be called would perhaps be priced between the 2 - you would then be in a similar dillema whether to spend the extra ~$150/- to get that camera or the 60D