We'll finish our present campaign first. This should last a good long while, so it will likely take us a year or more into 4ed - almost long enough to wait and pick up 4.5
The real question for us will be whether we switch once the campaign is finished or whether we stick to 3.5 and there's no real point in speculating about that as whatever my opinions are now may well have changed by then. I may well join an online game as part of D&D Insider, however, just to check out the new system and everything.