My conservative side leans toward, "until proven otherwise ....", it has to be Toronto.
Sure, the Kawhi swap could blow up in their face. But for the moment, on paper, we have to assume he's healthy and going to play to the best of his ability (contract year, after all).
So, on paper, given that they were the #1 seed last year, and they replaced DeMar with a better player and didn't otherwise suffer any huge roster losses, they should still be one of the top 2 or 3 teams in the East.
It's easy to make fun of their short playoff run and quick dismissal by the Lebrons, but they are still a very tough roster and if healthy and motivated, Kawhi makes them a lot more dangerous.