I am eager to see what happens at BOS as well. I agree that they probably won't do anything for a couple of years, until the integration of AA and US is complete. At that point United would have to swap with either old AA or old US to allow them to move into United's brand new space. I am guessing United will be VERY reluctant to do this, so the question becomes how much leverage does Massport have under the terms of their lease to force the issue.

Having said that, it won't be the end of the world for the new (post-renovation) status quo to be maintained. While new AA would not have a contiguous footprint, all their gates would be in the same terminal, post-security, and would be relatively easily accessible to one another. Furthermore, it's not as if BOS is a huge domestic connecting hub (or is ever likely to be), so O&D traffic won't really care that the gates aren't contiguous.

So, my base case expectation is that new AA will have a non-contiguous footprint within Terminal B indefinitely, with UA in the middle.

The bigger question for me is whether new AA ramps its BOS schedule back up to compete with B6, to whom it ceded significant market share when it cut back BOS as part of its "Cornerstone" strategy. In theory, BOS could become another hub for new AA, with at least a partial focus on TATL travel. BOS is the largest MSA in the country (at #10) that is not a hub for one of the big 3, so that might be an opportunity. On the other hand, hubbing TATL connecting traffic is a similar role to that which PHL will play, so perhaps it will be unnecessary and therefore BOS as a hub will be unsupportable.