My T2i sure hasn't. I bought the body-only new for what? Something like $850 when they first came out? They go for $450 used all the time now. Factoring in the difference in eventual resale value between the T2i and the 7D, it probably would have made sense just to buy the 7D to begin with.
I think I lost $350 or so when I sold my 5DM2 (last year).
Sadly, I have to agree - the T2i has dropped like a bag of hammers. I'm just going to end up keeping it as a B cam/crash cam.
And I'm guessing you'll see the Mark II drop just as soon as an affordable next gen FF camera hits - either the Mark III, or the rumored ones from Nikon and Sony.