I mentioned this over in the Skyfall review thread, but wanted to create a new thread for discussion as the film goes through production.
Apparently, Mendes is 75% sure he'll return to direct, and is waiting for the final script to be turned in.
Craig, Fiennes, Harris, and Wishaw are all signed on to reprise their respective roles. If Mendes returns, surely we'll get Deakins and Newman again as well. This has suddenly become one of my most anticipated films.