It's possible, but of course no one can predict the future. I don't think it's likely that you're going to see a 'fire sale' on this generation of PJ's, at least until they're about to be discontinued in favor of a new model and they want to blow out current inventory.
On the other hand, I fully expect that for the most part the next generation of 720P units will be priced substantially lower to be competetive, but frankly I think that the days of 720P projectors as a major player in home theater are numbered. It'll probably hang on for a few more years as 'budget' technology, and will quietly go the way of the dinosaurs. Once 1080P hit 1K it all but became inevitable, as this is a sweet spot for a lot of consumers curious about/ interested in this hobby.
Just my 2 cents, but 2 cents based on historical trends.