Not really. What do any of them have that we really want or need...?If the goal is to acquire & eliminate a competitor, shouldn't US be making a bid for Jetblue, or Airtran, or Spirit, or even SW? These competitors pose more of a threat to US than DL. Isn't DL a weaker competitor than most of the aforementioned carriers? Sure none of those are for sale or in bankruptcy, but money does talk... ... ...
Granted, you would gain market share in a few secondary markets, but nowhere near the presense that Delta would offer overall.
It would be more like USAir's acqusition of PSA (which gave us west coast market access, but not control). It would not give us any increased strength against our real competiton in the future... The remaining "Big Two" legacies.
And the vacumn of a missing low cost operator would quickly be filled in by another low cost operator. (like SWA replacing PSA in California) It is much more difficult for a legacy to enter a primary market, and take on the established carrier than it is for a LCC to "cherry pick" point to point.
Legacies compete from their Hubs (ATL is our main competition for CLT for example), and that competition is already limited by geographic and political limitations. (Think of ORD as a competitor for ATL).
IMO it is the endless competition for the higher revenue passengers (via RJ's) that has had as hard an impact on the bottom line as has LCC's competition for the lower revenue passengers.
And when you think of RJ competition raiding U's market share, one Airline comes to mind.