Durant is most likely going to re-up in Oklahoma City for a year, since the cap goes up by a lot again next year. That also synchs his free agency with Westbrook's, gives him one more season to see what the Thunder can do and assures himself the largest payday. The Thunder were, in my opinion, the third-best team in basketball this year...it isn't futile to see how things shake out next year when there are other rewards in play, as well.
He might consider Golden State and San Antonio, but I think ultimately he stays one more year in Oklahoma City.