This looks a bit tricky to me.Does it matter that the termination clause in v1.0a specifies that all sublicenses shall survive the termination of this License? Does this mean that OGC contributed prior to signing up to v1.1 remains usable?
Suppose X is a party to the OGL v 1.0/1.0a with one or more licensees.
X now enters into the OGL v 1.1 with WotC. They thereby renounce their rights under OGL v 1.0/1.0a, and promise WotC that henceforth they will use v 1.1 as their licence.
X is still bound by their promise to those other licensees to permit them to use X's OGC under the terms of v 1.0/1.0a. Prima facie, though, if that takes place then X is breaching their promise to WotC under v 1.1
However, if WotC is also a licensor to those other licensees under v 1.0/1.0a, then it has made the section 13 promise to them. Which means that X's prima facie breach of obligations to WotC is not actually a breach, because WotC has promised the other licensees that it can happen.
What is a bit weirder, though, is if those other licensees are not licensees of WotC. For instance, they might be part of a non-WotC-owned-SRD-derived ecosystem. In that case, WotC has not made any promise to them, and so X cannot honour both X's obligations to WotC and X's obligations to the other licensees. So in this case, it looks like X breached their licence obligations to those other licensees when they entered into v 1.1 with WotC.
I've worked the above out as I typed it, so I don't promise that it's the prize-winning answer to the exam! It's more of a first attempt to work through your question.