I wouldn't rule out this happening in some capacity on draft night. If the Celtics are sitting at #4 in the draft, and Knicks are sitting at #1 or #2, it is possible that the Celtics would Draft Stein (Center), send him to the Knicks with the 2016 Cavs pick, possibly another player, and get Okafor or Towns & Jose Calderon (could eventually become another asset--if he plays good and elevates his trade value, or when he becomes an expiring contract).
To trade up to land a guy like Okafor or Towns we most likely have to part with players like Sully or Olynyk as well.
I think Phil Jackson would be an idiot to trade the 1st or 2nd pick pick of the draft for anything short of a star player (Demarcus Cousins?)
Also, if the Knicks want to get rid of Calderon, they could just use stretch provision on him.