Personally, if Sony stopped their support of the Reader tomorrow, it wouldn't bother me one whit, since I so far haven't purchased any content from them. Fictionwise has been my source for E-Books for years, and I expect they will continue to produce Sony format books for multiformat books even after Sony drops it. I also tend to pick up a lot of free books from various sources.
It is going to be interesting to see what happens when Adobe gets into the market and what kind of support they get. If they do things right, they could very well create a standard themselves, and maybe make some of these formats obsolete. It could be a boon for Sony owners, especially since they seem to be working with Adobe.