This trade is not all that surprising. Something along these lines had been speculated all over the place (albeit in the midst of much other speculation). I had said earlier that Durant and Harden should be lethal together, almost no matter what you put around them. I think Durant is about the perfect star to pair with Harden from a personality standpoint.
My main point though is that I think this has been close to final for enough time that Kyrie knew it was coming. That is why he has quit on the team. As much as Durant is perfect to pair with Harden, Kyrie and Harden are the polar opposite of a perfect pair. I predict Kyrie is going to be traded, maybe to the Knicks or how about to Charlotte for Terry Rozier and others (Nets can take back 3-4 players to make up for the loses in the Harden trade).
My understanding is that he has a 15% trade kicker which I doubt he will waive. He is not going to be happy to stay and play with Harden, and he is not going to be happy to be traded. He thought it was just going to be him and Durant, best buds. Now that is gone. I suspect Kyrie is in a very dark place right now.