Might be too low of a market especially for tv which is what the NFL cares a lot about. Could also end up with another Dolphins or Jags situation where the huge college football fan base barely transitions over for a pro team support after a while.
According to this list, San Diego is ranked #28 in the nation while Oklahoma is ranked #45 in terms of tv markets.
http://www.stationindex.com/tv/tv-markets