Note that I said *I've* never found the 50's AF to be particularly lacking for action/sports. I never said anything about anybody else's situation. Since the OP never mentioned anything about the 1D4, I'm not sure how it even plays into this conversation. It's in a slightly different price range than the T2i/40/50/7D the OP asked about.
1. I did notice that you said the 50D was sufficient for you. However the OP was asking whether people thought the 7D was a worthy upgrade over the 50D/40D. By responding at all you are implying that the 50D af performance is could be sufficient for the OP was well. In short, by responding at all, you are saying something about "anybody else's situation."
2. As for the 1D4, the logic goes something like this: If the 50D af is sufficient, the 7D (which costs more) af is over kill, thus the 1D4 (which has even better af) must be only for loonies!
3. Don't take my comments too seriously.