There will be a new xbox, but not for another 18 months at the earliest according to something I read.
In terms of games now, future releases, online services and number of players online, the 360 is streets ahead of the PS3 and will remain so.
If you buy the PS3 you're forcing yourself down the Blu-Ray path, look at Sony's track record on "new" media. Remember the Betamax and the Mini-Disc? Blu-Ray will go the same way as the Betamax as Sony have stated they will not allow pornography on Blu-Ray like they did with Betamax. Guess what is responsible for he vast majority of DVDs these days?
I'm not saying that HD-DVD will be any better, but with the 360 you at least have the choice of upgrading and it's less than �130 - try finding an HD-DVD player for that money anywhere else.
If you enjoy playing online or want to start, then the 360 is your only real choice. Xbox Live makes it very easy