I don't see Virgin America merging anytime soon, simply because its already one of Branson's 350+ subs. Possible 49% stake ? Possibility. I don't see DAL putting that tip in though. More likely Alaska or Frontier who have the cash, motivation, and ability to profit + in that direct market. The 'majors' already have a reasonable "margin" on coast to coasts between LAX & SFO.
p.s. is UAL "p.s." still operational ?