I guess the best answer is, how bad do you hate your old equipment ? if you are just wanting to upgrade, then upgrade. If you still like what comes out of the speakers, then you might want to hold out till this time next year.
there will undoubtedly be a major shake-up in industry between now and next Christmas, so anything you buy risks not being up to "state of the art".
the flip side is that
a. you can keep telling yourself this same story every year and never buy anything
b. most of the coverage from the big show in Las Vegas had the receivers getting HDMI and such, as opposed to sound improvements. They had to be using something today to drive the HD-DVD and BlueRay equipment at the show, so at least some backwards-compatability must be built in to the new toys.
c. Anything that does come out this year will be geared to the gotta-have-it-first audiophiles and be hideously expensive and potentially unreliable.
the bottom line is, suppose you do buy something moderately pricey and of good quality this year and some thing worthwhile, reliable, and affordable is available in two years. you could always move this year's toy into the den.. or give to the kid as he goes off to college... or bring the parents kicking and screaming into DTS... if you are buying for the long haul, I would say wait. if this is just another step along the great electronic shopping experience that is life, fire away.