My wife and I would both like to think that I could become a single console owner for the next gen, but it just doesn't feel possible.
I've already got my 360 and I love it. I love the controller and Xbox Live and I can't imagine the competition being better in those two areas. I also must have it for exclusives like Halo 3.
The PS3 seems like a must have because of the Blue Ray HD-DVD capabilities. I would love to have an HD-DVD player and this will be my best option for that price. Then you have the actual game console and there are obvious reasons to own one for the games as well. Gran Turismo 5, MGS4, Killzone, etc, etc.
The Revolution seems like a must have for two reasons. First off, it's always gonna be home to the Nintendo exclusives and many of those are must haves for me. Second, being a 20+ year gamer, there is no way i'm gonna pass on the chance to play games with this brilliant all new control technology.
So, no matter how I look at it, there seems to be no way that i'll be happy just owning one of those consoles. Unless our financial situation demanded such restraint, I doubt i'd ever be able to not buy all 3.