It really is something of a quandry, because from a 3PP PoV, it's increasingly likely they will move away from the OGL after this for fear of WotC trying to throw their weight around again in future.
However, there are 20+ years of materials licensed under the OGL, in a tangled spiderweb of rights to seperate out if you want to publish them under any other license. For arguments sake, lets say I released a product in 2010 that referenced ten other OGL works, attributing them all correctly under section 15. I cannot unilaterally re-release that product today under ORC, because I do not have the right to release the other ten works I reused under OGL under the ORC license without the permissison of the original ten works owners. Assuming I cannot simply call those ten other publishers and get them to re-license under ORC, I now have to excise those parts that were not 100% my own work - which could prove difficult in actually remembering what those parts were (Was it this spell here? What about that monster there? Is this Feat one of mine? Perhaps I did something as simple as reusing an attack type from someone else's monster for one of mine) , and involve going through the entire text with a fine toothcomb to sort that out (because chances are I do not have a neatly annotated source file with every block of text backreferenced to its original source - something I actually do try to do nowadays, but didn't ten years ago) Which means it's far simpler for me to just leave that old product as-is, under the OGL, and only use ORC moving forwards. This means, of course, that my original work remains closed to reuse by ORC publishers - including myself.
Not every product is this complex, of course - many depend on nothing else, or just a small number of works that they know they can get relicensed to them under the ORC for reuse. But many are complex, referencing large numbers of OGL works in section 15, and the problem is that those are potentially lost for reuse in future ORC works because we can't rely on getting ORC licencing for every single dependency, or having the time to go through and remove those dependencies.
The point I think I'm trying to make here, is that it's always a simple binary "OGL or ORC" decision. It is a binary decision, but by no means simple. Some works will remain locked into only being usable under the OGL, even if their creator wishes otherwise, due to the interdependencies on other works. We've spent 20+ years under the assumption that the OGL 1.0a will be around forever, without a single threat of it ever disappearing, so we were fine building that interdependent spiderweb of collaborative work. Now we're suddenly confronted with a threat (whether legal or simply through WotC throwing its weight around in ways we don't have the resources to fight) that it could, and face a choice of whether to continue and hope we're okay, or throw away much of that 20+ year legacy of collaborative effort to start over with brand-new ORC-licensed works written completely from scratch.
I also think it's almost inevitable that some people will not take the necessary care and attention, and that some rights will get trampled on as some publishers try to redo past works under ORC. Probably a relatively small number, but the sheer amount of works involved and the fact there are still people that publish under the OGL without a full understanding of what it does and does not permit, means it's going to happen somewhere.
Personally, I do not think it worth trying to republish the majority of those existing OGL works (and I mostly mean the 4-8 page shorts by numerous 3PPs here), as it's far too much bother for what is likely to be only a small number of sales. But that does mean they will be lost to the ORC community.
