Based on AA's actions, in terms of growth, I'd group the hubs into 3 tiers:
Tier 1: DFW, CLT, DCA - have seen the most growth recently and are listed as most profitable hubs in their presentation slide show
Tier 2: PHL, MIA, PHX, LAX - have seen slower growth, some cuts, but still play an important role in AA's network
Tier 3: JFK, ORD - have mostly seen cuts. When AA decides to close a hub, one (likely JFK) or maybe both are likely candidates