VX will fly the A320 with 12 F seats (quite nice too) while AA will continue with the an F/J product line, offering 39 premium seats (soon to be 40). Add in the UA PS product with quality F/J seats.
I just do not see VX displacing AA (or UA for that matter) from this the transcon routes. There is just too much demand.
As a former UA 1K, I see UA as suffering the most given they are the weakest link for those traveling Y class in the NYC - SFO market..
UA has the smallest presence in the NYC market. Unlike AA, DL and B6 which all have hubs at JFK, UA has dismantled their former JFK mini hub in favor of IAD. UA has a poor Y class product (depsite the PS branding) and typically has higher NYC-SFO fares vs AA.
UA has essentially abidicated the NYC Y class market and I cannot recall the last time I saw a New York City specific UA ad (as opposed to a general national ad) in NYC (print, newspaper, billboard, TV or radio spot).
Meanwhile, DL is bulking up their JFK hub, AA adding is a flight and will soon fully occupy an new (if uninspired) JFK terminal and B6 recently entered the market with MRTC, DTV, a customer committment and newer planes than UA. Soon B6 will have a new JFK terminal as well.
For Y class pax, UA's vaunted PS service has been downgraded and IMO less comfortable or entertaining than B6's cabin.
UA might as well just convert their 757s to all F and C configuration given their neglect of the Y product in this market, or use 737s configured in F and C class only.