No, they absolutely cannot, under no circumstances ever
"the Contributors grant You a perpetual, worldwide, royalty-free, non-exclusive license"
I mentioned that in the post you're replying to. That's an obligation that arises between WotC and any licensee. If you have not taken up the licence, though, then you have no legal rights against WotC, and they can retract the offer of the licence at any time.
no, the license does not allow for this
You seem to be treating the OGL as a statute. It's not. It's a private law offer made by WotC to potential licensees. Like all private law offers, it can be retracted at any time.
I'll ask: are you a contract lawyer who is making an argument that WotC is in some fashion bound not to retract their offer? In that case I'm very interested to hear the argument: there may be some extra context, particularly some element of US IP licensing law, that I'm ignorant of.
But as I'm reading your posts, you just seem to be confused between
making an offer and
entering into a licence agreement. The latter imposes private law obligations; the former doesn't (leaving aside subtleties like estoppel etc), unless the offer is accepted thus creating an agreement, and can be withdrawn at any time.
They cannot stop making the offer either, they offered it once and they have no way of going back on that, unless they come up with time travel. Once something has been released, it stays released.
This is not a license both sides need to agree to, so WotC has no way of preventing anyone in the future from using that license for the stuff they published under it.
None of this makes sense to me. Of course both sides need to agree to establish the contract. The OGL v 1.0/1.0a even has express sections dealing with offer and acceptance and explaining what the consideration is that flows in each direction (sections 3 and 4).
WotC don't need time travel to withdraw their offer to me to license my use of the 5e SRD. All they need to do is, here and now, withdraw the offer. Given that I have not entered into any licence agreement with WotC (I have never distributed any OGC under the terms of the OGL), I have no legal rights against WotC.
If WotC were to withdraw the offer, and then in the future I wanted to use OGC under the OGL, I would have to enter into a licence agreement with someone else who is still making the offer. Which would be anyone who has entered into the OGL with WotC or any 3PP, and is obliged to make a standing offer (unless all those who they have contracted with were to release them from that obligation).
This is why, as I said in my reply to
@FrogReaver, there is no
practical reason for WotC to withdraw their offer in respect of the 5e SRD.