I'd settle on a budget first and then see how your options narrow, and ask yourself the following...
- How happy are you with the 40D?
- Are any of the 50D/60D/7D features really going to make your images better or shooting easy or more enjoyable?
- Is HD video really that appealing?
- Could you pick up an inexpensive HD Flip-style camera for much less than the price difference in the 40D/50D and the 60D/7D?