Do you ever have reason to shoot with two bodies? If so another 40D/50D to use as your primary and when hot shoe is required, along with your old 40D as a backup and/or second body might make the most sense and help you get to your glass upgrade sooner as well.

All that said, I'm a Nikon shooter who started with a D50, moved up to a D200, down to a D80, and then back down to a D50 again, so I'm not a big proponent of chasing the latest/greatest in bodies (plus Nikon has crippled every body since the D50/D70 with slow 1/250 flash sync for the sake of a simpler shutter mechanism).