The $12.5 billion Lakers deal is a bet that sports TV will keep booming. The NFL may test that.

Luke Hales/Getty; Mark Baker/AP; Getty Images; BI Prices for TV sports deals almost always go up. That's the rationale for Bob Iger and Josh Kushner paying a record amount for the LA Lakers. But over at the NFL — the dominant force in TV — there are signs that the rise won't go on forever. Bob…