IF Alliance have bought up sufficient spares (and additional airframes to cannibalise bit by bit) to last them the next 10-15-20 years...whatever...AND they can maintain reliability to a degree no less than their competitors AND the F100 doesn't become unpopular with the punters then indeed Alliance should be on a solid footing for a long time to come.
One does hear stories of F100 engines being run around de-rated all the time to extend life due lack of spares etc - is Alliance immune to such considerations?
Of course if the owners decide Network etc don't have to make a profit (or even break even) and offer A320's for the price of F100's...