1. There's no indication that WotC intends to back out of the OGL at all.
2. If they did, they could not take back what has already been released under the OGL.
3. If they did decide to be a pain, a lot of publishers would have a serious case to make -- i.e., private and public assurances from WotC managers that the SRD *would* be finalized led publishers, relying on those promises, to invest in various books.
4. If they decided to cancel or sharply restrict the D20 trademark license, publishers would be able to continue to sell existing materials at least for a time. During that time, all the publishers would come up with some kind of logo or something that communicates "Imagine this were a D20 System Logo."
It's WAY premature for anyone to be worried. When I walked out of the room at the GAMA Trade Show in 2000, where Ryan Dancey had just presented the Open Game License concept, I commented that this was the way that D&D could be run as a profitable business with about 4 employees -- once you have the essential books out there, just reprint them (with occasional revisions, probably by freelancers), let third parties publish the low-margin support products, and let the money roll in. I don't think we're quite at that point, but the reality is that with fewer employees WotC/Hasbro has *more* reason to want to see the Open Gaming scene vibrant and healthy -- because it keeps the gravy flowing for the high-margin core products.
That's how it looks to me, anyhow.