There have been several developments of late with regard to potential temporary venues in the Los Angeles area for either the Chargers, Raiders, and/or Rams. The first is the location there will NOT be a team playing. That is the Rose Bowl which has opted out of the bidding.
The second development is the LA Coliseum has said it will be bidding to be a location for a relocated NFL team. But with the Rose Bowl out of the picture, that leaves just one football stadium in LA to house a team.
LA Coliseum is where the Raiders played during their 13-year run in Los Angeles and indications I have received are that they are not keen on a Raiders reunion. That makes the Rams or Chargers, should either or both of them relocate, as the Coliseum's preferred temporary tenants.
While that doesn't entirely rule out the Raiders calling LA Coliseum home again, it makes it unlikely.
The next potential options are Dodger Stadium (56k), Angels Stadium (45k) in Anaheim, and StubHub Center (27k) in Carson. The best of those options may be Dodger Stadium, but thus far there is no indication any of them are open to the idea.
Even without a solid option for a temporary stadium for the Raiders -- or which of the three teams will actually be making the move -- the league could begin securing prospective Los Angeles season ticket holders according to Sam Farmer of the LA Times.
Farmer predicts the league will begin putting together a priority list of potential season ticket holders for the Rams, Chargers, and Raiders this fall in order to gauge the level of interest. He projects they would ask for a deposit which he projects would start around $100. This deposit could either be refunded if/when the team relocates or be put toward the actual season ticket.
And for Raiders fans, that priority list is very likely be to see games at either a converted baseball stadium (which is not far from what they have always had in Oakland) or the very intimate StubHub Center which seats about half that of O.co or Dodger Stadium. If that were the venue, getting on a priority list could be a wise decision just to make sure you got a seat at all.