1) I don't believe ESPN will fold
2) Even if they did, I believe their parent company is still responsible for ESPN's debts and obligations
but if we assume hypothetically that ESPN and Disney/ABC completely disappear....
My guess is that the league would shop the Monday Night package elsewhere. Maybe TNT, maybe a streaming service, maybe FS1..... but IMHO - and I admit this is just guesswork since I do not know the intricate details of the TV packages - the cap would indeed be affected by the change in revenue. If the league got more revenue in the new deal, the cap would go up accordingly. If they got less revenue, it would go down.