I hope I am wrong, but I seriously doubt you will see fares on United like $59 to Houston once Southwest pulls out. Airlines match their fares in markets where they fly, that's why cities and airports love having Southwest as a tenant. I think you are getting ready to see airfares in Jackson go up significantly - pay close attention after summer 2014.
5 years ago you could fly to Atlanta, Memphis, Cincinnati, Washington Reagan, and Detroit on Delta out of Jackson - now its Atlanta only. Southwest had flights to BWI, Houston, Orlando, and Chicago Midway and those are all gone or will be by June.
Once American and US Airways complete their merger you will have 3 airlines and 6 non-stop destinations out of Jackson. I think the Washington DC flight will be at risk due to US Airways and American having to divest service at Reagan Airport as part of the merger though I know our congressional delegation will lobby hard to keep that one for their own convenience.
American - Dallas
US Airways - Charlotte, Washington DC
Delta - Atlanta
United - Houston, Chicago
That's a pretty poor lineup when you consider markets like Pensacola and NW Arkansas each have 10-15 non-stop cities.
This is entirely correct. Once Southwest leaves, airfares will increase in Jackson. The capacity left behind will never be completely replaced either, nor will the number of destinations.