The fact of the matter is that nobody has a crystal ball, we can just make educated guesses. I try to rationalize about why/what/when of this:
-AE has a real senior pilot group (expensive labor costs compared to other regionals)
-AE flies outdated aircraft that and inefficient and expensive to operate (Saabs are breaking everyday, ATRs same, 37/44 seat RJs that arent efficient)
It would take a huge amount of cash to continue to run AE at the current state, and an even larger amount of money to buy new, more efficient a/c. The pilot labor costs arent going to drop anytime soon, unless you can take the top 1500 pilots and get them a job somewhere else.
I think AMR will contract several regionals in the next few years to fly portions of the current AE routes. It will be much cheaper for AMR and make money for their shareholders(pilot costs would be cheaper, equip would be larger/better). For AE pilots I expect the overall pilot group to shrink through attrition and the upgrades will remain about the level they are at now (7 yrs). In the end I expect AE to be primarily a DFW and ORD based carrier flying some 50 seaters and a few 70 seat CRJs.
As for Xjet, I think they are having a set of their own problems, but the pilot group is rotating out because CAL hires large numbers of XJet pilots. If I had to chose between the two I would go XJet.