If the Vikings move anywhere, it will be LA. Minnesota is running neck and neck with Indy to see which city/state will be stupid enough to let their NFL franchise slip away.
The SA rumors started years ago because Red is from SA. The more likely scenarios are Red selling to a LA interest or selling locally to the T-Wolves owner.
There were economic feasibility studies done years ago by someone (can't recall) that suggested SA would have extreme difficulty supporting an NFL franchise due to things like small corporate base (who's going to buy the luxury suites?) and to some degree the amount of disposable income among residents (who's going to buy 50,000 + season tickets?) - even though it's one of the largest cities in the country in terms of population, I doubt if things have changed much - plus now there would be a new stadium requirement (Alamodome won't cut it), and other things I can't recall at the moment. I don't think the proximity to Dallas and Houston was an issue in the study necessarily but SA is a huge market for Jerry Jones and an emerging market for Bob McNair and for some reason I can't see them supporting such a move. The study was done in the mid-90's, I believe, when Bud was shopping the Oilers for the last time.
My point is that if an existing team moves somewhere in the next few years, it will be either the Vikes or Indy to LA, because both have stadium issues and the league desperately wants a team in LA to re-tap into that huge TV market.