Are you wanting a DSLR or just a camera with interchangeable lens, because the only camera you listed that's actually a DSLR is the T2i. It would also be the first I'd knock off the list, because it's autofocus is not continuous and that would be a big negative for what your are wanting.

I'd wait for reviews of the Nikon D3100 or you could look into the Sony A33. They Panny might be very good for what you want, but I'd like to see how the D3100 does for tracking autofocus with video, since it's the better still camera.