If he leaves to go anywhere, it will not be for a team with superior talent, unless it's the Warriors.
If he leaves to go anywhere, it will be for a few reasons.
1. To go home. Although I don't think this is as big of a draw as some fan bases want to think.
2. To get into a better scheme - wide open, versatile scheme would be perfect for Durant. (Bulls, Hawks, Mavs, Spurs, Pacers, Celtics)
3. To play for a better coach (Spurs, Warriors, and Celtics all come to mind, with Hawks, Mavs, Pacers, Bulls all potentially there too)
4. To play with a different kind of teammate - more of a ball movement, unselfish style of teammates (Spurs, Warriors, Celtics, Mavs, and Hawks).