I think creators have a lot more power in this situation than theaters did with TWT. Proven creators like Nolan or Jenkins would still have other people bidding for their movies should they choose to walk (see: the wild auction for Cleopatra), whereas theater margins are so thin and the pandemic so ruinous for their finances that boycotting even one studio would be untenable, especially a studio as big as Universal. Sure, money talks, but other people have money too. And besides, this whole dispute is partially about money; WB pushing movies to HBOM potentially harms Box Office, and many top creatives are paid based on BO (EDIT: I see you address this in your reply, and I agree that Warners will probably be able to smooth out most of their relationships eventually.)
I'm not saying creatives will boycott WB forever, to be clear. But I expect to see more Cleopatra-style snubs for WB. At the very least, working relations are going to get very awkward. They might even lose a key producing deal, like Atomic Monster.