The Pacers took the Heat to 7 games; I'd say they're definitely championship material. Then consider Paul George is only 23, Roy Hibbert is only 26, Lance Stephenson is 22, and they're surrounded by solid veterans (Granger, West, Scola). If Hibbert can bring his game to another level, I can't see many defenses stopping him.
Anyway, the Pacers aren't the only example of not needing to tank to be competitive. Apart from the Spurs and Thunder, most of the championship contending teams were built through trades, free agency, and late round picks. Houston, Brooklyn, New York, and Memphis are examples (and although Memphis did tank at one point, their current nucleus sans Mike Conley was not a result of that). Don't forget Miami too.