The reason WotC has gone forward with OGL 1.2 is all about interactive software. It is entirely about s. 1(b):As far as I can see, the only way this ends up in court is if a big player continues to rely on OGL 1.0a
"(b) Works Covered. This license only applies to printed media and static electronic files (such as epubs or pdfs) you create for use in or as tabletop roleplaying games and supplements (“TTRPGs”) and in virtual tabletops in accordance with our Virtual Tabletop Policy (“VTTs”)."
If somebody does something in reliance upon the OGL 1.0a in relation to interactive software? Then the litigation risk is significant, imo and is certainly the kind of risk that a prudent business person should take into account when conducting their affairs.
Shy of that? Probably not. We can quibble about the nature and degree of that probability and how it affects somebody's risk vs reward equation, but that decision is ultimately up to whoever decides to rolls those dice and take that gamble. It's a business decision, not really a legal decision. And it's one that isn't up to you or me.
So if Brilliant Thief Games LLC decides to release a new archetype and related rules for PF1 based on the Alchemist class, say, and relies upon OGL 1.0a and the 3.5 SRD as authorizing that in whole or in part on DriveThru RPG, are they going to get sued?
No, probably not.
If Paizo were to do that instead, (and to be clear, they have no commercial interest in doing that) would they get sued?
No, very probably not.
But if Foundry Gaming, LLC, say, decides to release Foundry VTT 2.0 for 5e and purports to do so under the OGL 1.0a? Then it's probably time to unlimber the guns and get ready for war in court.