I actually think US has a decent shot at DCA-SJU service. There is apparently a lot of support for that routing from both ex-pats, the SJU government, and a lot of the travel industry.
While a lot of "entrant" carriers are out there, I think that there is a conflict in DOT's ideals: 1) allowing new entrants into the market conflicts with 2) permitting connectivity at the destination airport.
AQ might get 1 to SNA.
UA would get 2 to SFO.
AS would get 2 to LAX.
US might get 1 to SJU.
I don't think that Primarius would get anything as they've not proved that they can yet move a single passenger.
I think that there are also a number of "in perimeter" slots available. I think that US has an excellent chance of at least half of these since US has a proven track record of supporting and utilizing the additional slots given to it.