Unless Durant's acquisition hinges on Butler, Bradley and Isaiah are going nowhere.
Butler is a top 20 player in the NBA, but Bradley, Isaiah, and #3 is a gross overpay for him. As a standalone acquisition, it's a backward step; and, on the court, it's a lateral move. If it's going to take that type of offer for Butler, I would pass.
Bradley and #3 is a solid offer for Butler that few teams will want to match, throw in one of Rozier/Mickey/future BKN 1st and it should be a done deal (I would try to hold on to Rozier like the Clippers held on to Bledsoe in the Paul trade).