I don't think Opposition Agent will get banned. Restricted? Probably.
But I don't see it getting out right banned. The reason Lurrus was banned because just restricting it didn't solve the problem it was causing.
Opposition Agent can still be interacted with, and it dies to removal, so there's some balance.
I think there will be growing pains to start, but I think unless maralen of the mornsong starts being a common cEDH monoblack commander, it'll be nothing more then salty tears, not a broken game.