IMHO...

Why would a legacy buy one of the LCC carriers? If the LCC's have any valuable slots into NYC or other slot controlled airport, the DOT makes them give some away to make the deal go through. Realistically, that would be the main reason to merge with a LCC. If you do it to stifle competition, it's pointless, another one will spring up out of the ether to take it's place. Money's cheap, oils low, and barriers to entry are minimal.

So in the end, if any of the legacies wanted to go into the LCC business (tried to before, doesn't work because your a legacy cost structure selling tickets at a LCC price point) they could just buy a gaggle of airbus and saturate a bunch of point to point vacation markets.

By and large, the LCC's and Legacies are aiming for different customers and different segments of the traveling market.

Traditionally with oil this low for a period of time, the whole industry would go on a expansion fever, trying to garner that elusive market share. Then just as all the new jets and employees would be taking to the sky, the economy would turn only to leave the companies with huge capital outflows and minimal revenues.

This latest era of the industry has shown management that they don't need to recklessly pursue marketshare, but instead can get rich by increasing the companies profit margin through consolidations, limiting growth, and using JV's.

Also, the huge retirements at the legacies also make it increasingly hard to hire and train enough people to replace those who are leaving, let alone try and grow at any appreciable clip.