In my case it's irrelevant, since I have a little less spending room than I did a year ago, but I doubt my spending habits will change much. I'm at the least picking up the first round of books (PHB1, DMG1, MM1), and if my group is in love with the changes, I may pick up more. At the least, I'll have the basic set to run conventions with/run one shots, etc. if I don't like it.
I'll buy whatever looks interesting to me, whether it's a new 4e book, a book from any prior edition I don't have (should have marked Other!), or some third party book.
I have 3 month old twins thus my money for D&D has shrunk immensely.
So if they want my money, they are going to have to work a lot harder for it for the next few years.