You'd see little benefit upgrading the camera with portraits, but might appreciate better AF performance for motorsports or any kind of action photography. You'd have to go to 60D or T4i to see any significant improvement in AF performance. The T2i and T3i have essentially the same AF system as your T1i, I believe. There's little increase in resolution (15MP to 18MP), so you won't see a lot of difference in image quality. But the newer models would likely be a little more usable in low light, likely would give you about a stop higher usable ISO. 7D is great for action photography, but uses the same sensor and processing as the T2i, T3i and 60D (7D uses dual processors so it can shoot at a higher frame rate). T4i uses a newer processor, but essentially the same sensor, so won't really "upgrade" image quality very much.
Frankly, I usually respond "lenses before camera". Good glass makes more of a difference to your images. You already have some good lenses in the 85/1.8 and 70-200 (I don't have the 40/2.8, so can't say from experience). I'd definitely sell off the 18-55 and 55-250 kit lenses if you have no use for them. Use what you can get out of them to fund better lenses. That will make more difference to your images.
15-85 would be a better "walk-around" lens and give you a wider angle of view. Or 10-22 would give you a whole lot wider angle of view. You might also want to consider 50/1.4 for portraiture.... to complement the 85/1.8.
If it were me, unless you can cite a real need such as AF perfromance, I'd continue building a quality lens kit and let the camera body upgrade wait for a while.