Dumb question about timing a new desktop purchase

[The DaveR]

My current desktop is 2+ years old and its age is starting to show. I'm going to get a new one with just about everything maxed out and I wanted to know if I should just go ahead and do this now or if it makes sense to wait until the new Windows (Vista?) is released. The intent is to have a high performing desktop (for poker and music) for the next 2 years. TIA.