NWA likes to have a tight control over its regionals. Example, XJ and Compass both wholly owned by NWA. DAL learned from its experience, it needs to reduce 50 seat RJ flying and replace them with bigger jets to operate more profitably. If NWA/DAL merges, expect to see a major reorganization of regionals. Don't know what will happen to Skywest but for Comair, XJ, Compass, RAH/CQT and Pinnacle, there will be a major reorganization. NWA has already formed a Mesaba Compass Holding Corporation to operate XJ and Compass.
If SLC stays open as a hub, which I think it will, NWA/DAL will most likely keep Skywest but also bring in Mesaba and Compass and build up flying throughout the West. This is already happening for XJ and Compass. Gradually, NWA/DAL will try to balance flying done between Skywest and its wholly owned XJ and Compass. I don't see any reduction in domestic flying overall for NWA/DAL but merger may result in a net reduction in domestic flying for some regionals.
There is no such thing as an ironclad contract. If mergers goes through all bets are off.
DAL would probably want to increase it share of the international flying, especially to Asia via its merger through NWA.