That's the long-view of it, but in the short-term, the NFL wants to add a team or two to LA BEFORE the next round of TV contracts, in order to say "see, we have teams in LA, give us a TON more money." Later-on though you're right. The team(s) will lack support, games will be blacked-out, the networks will grumble, and they'll eventually move, but the NFL doesn't care about that.
If I were a current or prospective owner, I would NOT think about going to LA because it's a losing proposition, especially for an expansion franchise (with fees in excess of $1B). And then there's always the threat of a lawsuit from Al Davis.