If I'm not mistaken, trademark law would allow us to indicate compatibility, etc., something explicitly restricted in the OGL. That is, I can't say "compatible with D&D 3e" unless I have a separate license with WotC saying so. This is a consideration, yes?
Ditto, by using open content I have to allow others to use my open content.
OGL v1.0a is generous, to be sure, but does have considerations both ways. If it didn't, it couldn't be a contract or license, right? They get something, we get something. This is, if I'm not mistaken, a big part of the reason for token payments such as a $1 retainer to a lawyer, to establish client-lawyer privilege... a contract doesn't need to be objectively even, just acceptable consideration on both sides.
How does Section 9 measure up then, that says "if we update the license, you can continue to use whichever one you want"?
It seems to mean that (for example) if v1.1 says "v1.0a is no longer valid", but I do not accept v1.1 (and according to the license I have accepted, I don't have to) then v1.1 does not apply to me.
If they took it to a different meta level and revoked 1.0a 'publicly' then it seems clear I'm out of luck, but if it's done via a license I don't accept, does it still apply?
Hmm. Even then I wonder, if they stopped using v1.0a themselves even for stuff they licensed that way 20 years ago, but the license is still valid for those works and lets us sublicense, what does it mean for those cases?
(as you might have guessed, I'm not worried about 5e, I'm worried about stuff I've been working with for longer than 5e has been a thing...)