But again, if 5e backs away from the OGL, other companies will return to the 3e OGL, create an alternative that competes with 5e, splits the players, and 5e will flourish less.
I disagree. I think WotC's big mistake with 4e and the GSL was one of timing - they backed away from the OGL at the same time as they were producing a 4e that was... controversial.
With 5e, they've produced a well-received new edition
first and have already gotten the fan buy-in. This means that the loss of the OGL is less of an issue - there isn't a big body of fans currently in a wait-and-see mode for this edition.
Plus, it bears repeating (again) that what happened with Paizo and Pathfinder was a convergence of many circumstances coming together just right. There isn't really scope for anyone else "doing a Pathfinder" and coming up with a 5e-replacement, because there's no-one out there with access to a database of 40k magazine subscribers looking for a new home.
(Of course, some publishers may now scrap any 5e plans they had and instead publish their support material for Pathfinder instead. But I doubt that will make much difference either way - those people who have bought into the various games have now made their choice and are unlikely to be swayed by 3pp going one way or the other.)
It's probably only a matter of time before an OGL publisher ends up getting C+Ded over an error in a document.
Unless someone tries a wholesale 5e clone, I suspect WotC may well just not care (about books/PDFs anyway). If they don't release under the OGL, I would expect most 3pp to simply stay away, leaving only the few players we've seen publish already. In which case, they're probably not worth the PR hit.
(Two further exceptions to this: if someone engages in trademark violation, WotC will have to take action, of course. And they'll be stricter on electronic tools, as they'll need to police these to protect the value of possible licenses.)