Even if a certain regional has the cash (or can get the credit, whatever) to buy a legacy or not (and regardless of if they would even if they could) is all mental youknowwhatturbation until it happens, which it probably never will.

That said, what some mega regionals can and will be able to do is let their executive talent loose to play with airplanes in the real world. Even if they end up liquidating ala IndyAir, they will inflict significant damage to the very mainline that pumped them up for so many years, and they would have achieved that with the money the respective legacy paid them (so much for the savings of outsourcing huh?)

I predict exactly this for a certain mega regional if and when their constant growth gravy train ever leaves the station. They WILL get bigger airplanes and compete against the mainlines that sponsored their phenom growth for decades. They might succeed and do permanant damage, or they might fail and only do significant short term damage. But either way, no legacy will ever make or save a penny by doing business with them in the long run. But they don't teach that at Harvard anymore anyway so who cares.