"I have the impression that TV revenues are increasingly as important as gate receipts (and indeed had baseball figured this out back in the 1950s the Dodgers could have stayed in Brooklyn), and so perhaps population, distance, etc. may not matter that much."
Don't know that I agree. While I DO agree that television revenue is far more lucrative than the gate (witness F1 President Todt's comment that he doesn't care if there's a single person in the stands as long as the TV sightlines aren't blocked), having an active physical presence is important. In my opinion, if MLB had not moved to the West Coast, the PCL would have continued to dominate the baseball scene and, while MLB's popularity would have grown, it would not have come to dominate the market as it does now - especially with the boost having two legendary teams move gave the product.
I liken it to the NHL. Los Angeles had the Kings, and no other NHL team could survive in the west. When I was growing up, the closest team to the Kings was St. Louis - talk about grueling road trips! Then, the far-sighted and now all-but-forgotten Bruce McNall (OK, he had issues ...) traded for/signed Wayne Gretzky. Hockey popularity skyrocketed in LA, and before you know it you have franchises in Anaheim, San Jose, Vancouver, Denver, and Phoenix. Physical presence (especially a successful one) leads to popularity and fan base, THEN the national television revenue will flow.