Rumors of the demise of PHX as a hub have been going on for years and as of yet (what, 5 years in) nothing has really changed. There are some new routes and some have been lost, but AA out of PHX looks a lot like US out of PHX did, which is also quite similar to what HP out of PHX looked like. With the US / HP merger there was a big hope that PHX would start seeing some international destinations, but that never materialized. The same with the AA merger, but nothing happened... again.
Let's face it, PHX is a regional hub (at best) and as an economy is primarily reliant on seasonal tourism for O&D traffic. In other words, cheap fares. Sure there are a number of business travelers here and they do spend money, but not enough to warrant PHX ever becoming a real hub on the order of DFW, CLT, LAX, ORD, PHL, or any of the others. In that way it's very similar to DEN, but DEN has enough business traffic to support some real international traffic. PHX is a gateway to Mexico (at best) and as that it's still a vacation hub.
The LHR flight is promising and if it weren't for the fact that BA did very well here for a couple of years with an additional seasonal 744 service I'd say that AA's LHR flight is an indication of what could be on the horizon. BA isn't running that route this year and when AA made the original announcement it was for seasonal service that effectively mirrored what BA had been doing for the prior 2 years. The recent announcement that the flight will be running year round is encouraging, but I can't help but think that's either a precursor to BA terminating their service as they retire the 744s or a reflection of the fact that many customers are sick of flying on BA's old and tired planes.
I don't think that AA will ever drop PHX as a hub as it's a great place to move a lot of traffic east to west and north. There are rarely WX issues which cause major problems which makes it possible to move a large amount of traffic in from the east and distribute those passengers throughout the western US. Sure, they could do that at LAX, but I don't think that AA has the capacity there to be able to do that.
AA's redistribution of FA bases makes sense on a business level, but I seriously doubt it's an indicator that PHX will lose it's hub status. I seriously doubt that PHX will ever see an increase in service that could make it a premier hub so it's likely to continue as the utilitarian entity that it is now.