We keep hearing AMR/AS. However AS wants to remain independent and AMR would have to make a hostile take over attempt. Believe it or not, it's not something they want to engage in. As far as seniority integration, ALPA's merger policy is now law. APA thinks that it would go to arbitration and follow the template of the USAir--America West integration. In that case the arbitrator didn't "see" the USAir East furloughs, so they got stapled behind the most junior America West guy. If that's the case, you should have about 2000 guys behind you.
The other scenario is that will will try to play spoiler to a NWA--Delta deal, or at least try to make it a more expensive deal. And lastly, when the limits of foreign ownership are lifted, will we either merge with BA, or be bought outright by Emirates.
Of course, tomgoodman's scenario is also a good bet.