Well, I really doubt it would be next year, or the year after. And, I agree, don't buy launch systems unless you have a really good reason to. Every generation, systems break down more and more.
But, wait and see how things play out, you may not even want the next xbox, so, don't let that be a factor in anything. If you do want it, you can always wait, and see how well it does. 360 at the moment can't hold it's own against the PS3, and it may have damaged it's overall reputation. But, again, we wont know until we see how the system sales after it is released... and, if it's not before December 21st, 2012, I don't think it'll matter anyway.
Just don't let the next gen factor into your decision, the PS4 may come out later, or the next nintendo console.. maybe you'll want those more..