I don't think we're looking at another singular behemoth. I think that what might (might) happen is that the stuff that arose in response to the OGL self-own are games that, collectively, will be as big as Pathfinder.
Like I said, I don't think anyone here thinks that Paizo is going to put WotC out of business or has any desire to. But they take enough market share to make someone at Hasbro (irrationally) freak out, which is why we had the whole OGL debacle. And that freak-out, in turn, then created the exact opposite effect they wanted: Instead of everyone clumping together under WotC's umbrella (something that consumer goodwill would likely have done to large part in 2024, with the 50th anniversary), they have spread players out at least a little more.
Is it a devastating or "behemoth" amount? Absolutely not. But Hasbro wasn't freaking out about a behemoth. They lost their minds over the proverbial molehill. Creating a bunch more (littler) molehills was a problem they created for themselves instead of just switching to decaft and using that Breathe app on their Apple Watches that no one uses.