Let's see...there are xxxxD cameras, xxxD cameras, xxD cameras, 7D, 5-series, and 1-series cameras. Of all those lines, how many have reused sensors? One. Not coincidentally, it's the only line refreshed annually. Think consumers would pay the increased cost to fund development of a new sensor for the xxxD line every year?
Oh, and the T2i has phase detection on the CMOS sensor, right? :