Well, two strong reasons would happen:
-the players will to leave, like we are seeing in Juve's case, their top players left (only Buffon stayed, Del Piero is a "home" team and Nedved is in the end of his carreer).
-the loss of millions in TV rights, sponsors, prizes (from all competitions) and gate revenue.
I doubt the owners of the teams would want to pay all the debts.
They may like the club but they don't like to lose money.