my only concern about the 1D Mark III would be the potentially very low resale value.

Otherwise, based on what I've seen with a few MkIII bodies, they are worth a try. You can always return it or replace it if you see issues. The files from the MkIII are just so great compared to the previous generation...

On the other hand, if you don't have too much Canon glass and like Nikon's interface, and Nikon's lens lineup suits your needs/habits - then the D3 is really hard to beat, especially with recent price drops and the availability of buffer upgrade.

I've tried the D3 on a few occasions and while I love the output, I'm too used to Canon's interface, so I'm sticking with it...

If I didn't have the MkIIn, I'd definitely give the MkIII a shot.

But if you think that the 50d can hold you over, it definitely looks like a great camera, and waiting does make sense - afterall the DSLRs are only getting better and hopefully cheaper :)