First, I don't think it will happen. Timing wise, it was a protest and gambit against the new changes to the CL that have been proposed (and voted in today), and they were threatening to burn it all down in protest. The plan was for it to be to replace CL for them but in addition to their national league games, but when it means being banned from national leagues, then it becomes financially terrible, not advantageous. So from a self-interest perspective, it doesn't work--especially when fans reject it too. But I also think that governments will stop it, and of course there will be a legal battle with the UEFA and FIFA.
But if it did happen, football's dead and United would be dead for me. Feel like throwing out my shirts and burning them. I hope the fans picket outside the ground, the players go on strike and the coaches resign (did Jose walk?). They've declared war, and the football needs to fight back until these parasites are driven out of football.