If and when 4e is announced, do you know what that will do to my 3.5e purchases?
It will drive them through the roof. I don't really want to go to a new edition, 4e would have to be truly amazing and improve on 3.5e vastly for me to bother switching over, and I honestly can't imagine a D&D edition that would be worth the switch.
I'll buy 6 PHB's for a gaming group, since if the 3.5 PHB is going out of print, I want to be able to run it in the future, possibly for players who might not have it. I'll be able to finally catch up and be "complete" with my 3.x purchases and pick up all those books I was meaning to get, but more keep coming out.
I may well buy a 4e Player's Handbook (or Starter Box if the horrible rumors of a "collectable minis-based RPG" are true), but I don't expect to move over to it or regularly buy all the new books for it.