I observe that 1.0 contains the verbiage:
"Updating the License: Wizards or its designated Agents may publish updated versions of this License. You may use any authorized version of this License to copy, modify and Distribute any Open Game Content originally Distributed under any version of this License."
which at least to my open source license not-a-lawyer read says that they basically can't revoke it.
They can relicense stuff going forward under 1.1, and that may be bad, but I wonder if people are misunderstanding and treating it as apocolyptic when it's just bad. It seems like the worst case scenario is the community undergoes a de facto fork and you can stick to a 1.0 world if you want, not that all the 1.0 stuff goes away.
This smells to me like many similar panics in our community when some project goes to relicense and people don't generally understand that the relicense only applies going forward, because in general you can't retroactively relicense an open license. (There are nuances to that statement which I'm skipping over, but I'd say that's the most correct short summary. The thing that people think is happening is not what is happening.) Of course it is still valid to be upset about the relicensing going forward! It just may not be quite as much a kick in the teeth as people think.