In the East, I think the Bucks have the highest-ceiling "best case scenario with the current crop of players."
I'm tempted to say the Wizards, though, just because it's a relatively large market and they've got John Wall.
In the West, the Timberwolves have some fantastic talent, but I'm not ready to trust their ownership and who knows which coach they'll hire for the long term.
Given that, I'd have to go with Portland or Utah. Both teams have excellent coaching, modestly accomplished management, and a promising foundation for the future.