well i suppose it coincides with aircraft orders but a critical factor in upgrade time is the growth or reduction of the flying. AE has a solid chance of losing some its flying if AMR continues with the divestiture.
Also, and this goes with attrition, AE has a lot of guys that got stuck here with the AA flowback and the disastrous post 9-11 years, and a lot of these guys now have no intention of going anywhere for the rest of their careers. They're making close to $100k (I've never understood why that's a magic number for self-contentedness) and are senior and have the inertia of age. It's true that all the regionals have these, but AE has a larger contingency than all others. And this slows upgrade time because a significant part of the captain pool is not in motion.
If letter 3 stuff ever gets sorted out it could have a significant impact if career Eagle guys decide to go to AA. But that's speculation.
Anyway, if things continue as they are now, which never happens, I could see a 4 year upgrade at Eagle. Possibly, just possibly, as low as 3 or 3 1/2 although most of the low time guys won't even have the hours to upgrade in 3 years. There's definitely a large x-factor in there with the divestiture.