Legally speaking, perpetual does not mean irrevocable, it only means it does not expire. It is possible to have things irrevocable in a contract or license, but it has to be specifically called out in the text.

That said, it's still shaky ground. Courts look unkindly towards obvious bad faith. For example, Wizards themselves on Q&As have very strongly implied it would never be revoked. While the text of a contract is what matters, lying or misleading others is obvious bad faith. Especially 20 years later after allowing derivative works to thrive.

In any case, the courts have already ruled that game mechanisms cannot be copyrighted or trademarked. Creators who want to make stuff explicitly to be compatible with D&D (or any other game) cannot be stopped unless they use actual trademarks like names of things that aren't in the dictionary or public domain. If the court hears a case AND rules against WotC, it would be an absolute disaster for them, as the OGL will become completely irrelevant, poison pills or not, and One D&D will be cloned in real time with impunity.

I hope WotC is arrogant enough to sue a small-potatoes creator who successfully crowdfunds a legal defense and makes this dream come true.