Xbox is coming out first, they're doing a promotional preview on MTV on May 12. The Xbox will be out before Christmas and should have some decent games to start. Rumor has it that the "Xbox 360 / Xbox Next / Xbox 2" will feature wireless controllers and a silver finish, and there will be 2 models available. The better model might have a built-in hard drive and backwards compatibility with Xbox 1. Every new game will feature widescreen 16:9 support, high-definition video/audio, online multiplayer, and customizable soundtracks. Better yet, it will be released here first because it's a US company.
Not sure about details for the PS3 as of yet, but supposedly they are trying to build in Blu-ray DVD technology and better hardware than the XBox.
The Nintendo Revolution is furthest behind as far as when it will be released, but this might be an advantage considering they not only have more time for development, but they can also see the competition first (kinda like being the dealer in poker).
Anyways, I just pick this stuff up from articles so it's all basically speculation until we really see them.