I've found that I accumilate figures for fodder, through clearances, Ebay auctions, and yard sales at a much faster rate than I could ever hope to customize. This has both benefits and faults...the benefit is that I've built up a fodder "bank" of over 500 figures for customizing. The fault is that, like so many other people on the list, I'm running out of space to store the figures, never mind even displaying the collection!
As far as the future of customizing, I don't think SW toys will disappear entirely but probably will scale back and move away from the movies in an effort to tie into all the TV things that are planned. Customizing will continue, just as vintage customizing are still possible today.
My plan for the future? Learning to sculpt in wax so if the market dries up for new figures, I can make my own! I also have plans for lots of dioramas, as long as space allows for it.