But seriously, what is to stop AS from capturing West Coast POS to JFK & also from ANC?
Honestly, in this situation, I think it's just themselves. They pulled SJC-EWR for example and that's a route that has very high local POS here. LAX-JFK is going to be pulled in a couple months now, and while that specific route may be very "50-50" with planes full of pax from each city, odds are that if you're flying AS, POS is much more heavily weighted towards West Coast/LA area. And with their onboard product, I'm sure they could undercut nearly every other legacy on price if they wanted to, seeing how they fly high-CASM 321s/739s to the east coast whereas the competition is premium-heavy, lower-casm 321s and 767s.
Seeing how B6 has gone into secondary and primary cities in the west with a great soft+hard product in both J & Y, I think it's safe to say that they're the ones capturing a lot of the POS here in this situation (SJC, BUR, ONT, SMF, along with heavylifters SFO/LAX/SAN/PDX/SEA) etc.
Despite this, I really don't think it's in AS's best interest to pursue more tcon routes. Let AA take care of them - in fact, AA's 321Ts and 77ws fit the specific nature of the market perfectly, while AS's lower-yield, large Y config really isn't suited for the job as well as others. This is part of the reason I'm quite skeptical about AS bringing on lieflat tcon J - they are inherently a sub-premium carrier. Not to say they do not have a good inflight experience, or decent product, it's just that if we look at many of the routes they fly (for example they are very big in Mexico and love doing low-frequency leisure) and the seat counts on planes as of right now, adding lieflats would mark a pretty deep shift in the foundation of the company itself, as well as infringe on newlywed AA's slice of the pie.