Sooner or later the NBA commissioner will have to do something about it. He said publicly that he doesn't want how Durant demanding a trade after signing a huge contract. Sooner or later we will see some rule change, at least to have team owners get a better deal when they sign this kind of players.
And since they can't be simply be traded right away because the Nets wants more, and you can't blame them. Again, it boils down on the money they put in the line and they want something in return, like future draft picks, because that's what the lost as well when they sign the 2.
I do not think that there is a need for a rule change at all. I believe that we shouldn't really meddle with the teams inner works and let them do whatever they want with players. If a team could trade a player away without asking permission from the player, then I am sorry but a player should be able to get a trade from the team at the same time.
Let's assume that Nets got an offer a year ago, like something so special that it was amazing, picks and all-star players and everything, people thought that other team was idiot for offering, would Nets not be able to take that deal? Even if Durant wanted to stay? Of course they would have taken the deal. So if teams can trade players away, then players should be able to go away if they want to as well.