You can't revoke it but the question is whether it can affect future redistribution of pre-existing derivatives. The license appears to say so, but even if it does it may not be legal and thus would be voided.

Yeah, I understand it's complicated, but there is already a lot of FUD in the world about what copyright and licensing mean. The WotC/OGL discussion deserves a sober discussion by people who understand copyright and licensing, not going along with the fever emanating from places like Twitter.

You can if it's argued that the license was revocable, or forced to use new licenses. That's why everyone is angry, it's vague and who can afford to fight Hasbro in court when they use the vagueness to start a bully campaign against smaller creators first?