I look at it this way, their is always going to be a faster part coming out in X amount of time, no matter what time of year it is.
Build up a good budget, figure out the parts that you need for your computer so that it can do what you want it to do, and buy those parts at the best prices possible.
Just like someone else said on here, don't worry about having the latest and greatest computer parts. You'd be in debt up to your neck within a year if you did that.
If you did want to wait for what's coming out next, but not too long, you could wait for Nvidia to release their new video card line-up this fall. I think that's the only thing that's being released until '08.