Well, as long as hubs aren't closed, domestic feed will continue pretty much the same, with some regional flying consolidated probably. The growth will be from the INTL sector. If DAL and NWA got together, passengers could connect in ATL or DTW from one side of the world and truly hit the other side, all on the same airline. Delta has already added over 50 INTL cities last year alone, and there are plenty more to be added. Throw in 787s NWA will be getting, and the combo could prove a "do it all in one airline." That would force CAL to buy UAL to try to be the same, and the others would scramble too.
Seniority integration probably wouldn't be fun, but we have all learned something about USAir and AWA---becareful with binding arbitration. ALPA would have to come up with something fair, or we would have to go down the same arbitration lane as USAir/AWA did.
If DAL and NWA got together, the lack of overlap would keep the hubs and the jobs. With additional planes coming like 787s and 777LRs, along with current 744s, A330s, and plenty of 767ERs, INTL upgrades will continue. Domestic flying will maintain atleast the current size, with DC9s maybe getting replaced with MD90s or even E190s. Maybe MEM and CVG would see a slight reduction in service, but not enough to give Airtran or SWA a foothold.
Now if UAL and DL get together, I don't know what would happen. Lot's of hub closures, crying, cats sleeping with dogs, Tilton kissing everyone in sight, I don't know....?
Bye Bye--General Lee