What do people think the best case, realistic case, and worst case are? Don't have to answer all three lol.
WotC make a fulsome apology, issue an OGL1.1 that is that same as 1.0 but tightens the language guaranteeing that it is irrevocable, and over the next few months things revert to the status quo ante. I don't expect this to happen.
The damage is already done, and it doesn't actually matter what happens with the OGL.
WotC has burned a huge amount of goodwill, the enthusiasm for OneD&D has been seriously dented, they've lost an awful lot of their third-party support, and they've lost a relatively small but relatively vocal chunk of their customer base. The movie fails (not necessarily because of this - there was a good chance it was going to anyway). OneD&D is dogged with a low level of backlash throughout development, and releases to a collective "meh" as the bubble deflates. And we go from there.
Meanwhile, for the 3pp the outlook is pretty dire. A lot of the smaller providers shut up shop. The mid-level providers generally shift away from OGL, as it is no longer the safe harbour they thought. We get a number of competing "D&D substitute" games, but none really gets traction. Some companies go bust, a lot go on but with much lower sales generally (but the overall market share probably remains about the same - 95%+ WotC-D&D, 5% other - just a much smaller pie).
WotC double down on OGL1.1, have Kickstarter block any campaign that tries to use OGL1.0, and have OneBookShelf remove all OGL1.0 product from their servers (in the worst case, including already-sold items). Paizo choose to fight, and lose heavily, being bankrupted as a consequence. Emboldened by their win, WotC then sue EN Publishing over Level Up, and ENWorld goes dark as a consequence.
The former 3pp attempt to pivot away from OGL, but suddenly deprived of a market or funding they mostly fail.
And because of the backlash that results from all of this, the D&D movie crashes and burns, D&D sees a huge drop off in subscriptions, OneD&D releases and sells about as well as late 2nd Edition adventures, and D&D is stuffed in the Hasbro Vault of Dead IP.
Gaming as we know it comes to an end, and dogs and cats start living together. Oh, and it turns out that his weekly D&D fix was the one thing stopping Putin launching Armageddon.
I'll just note, I didn't say it was a likely