I think that might've been their intention but they don't have nearly enough draft capital/assets to trade for such a star player. AD and Lebron despite his age are both still playing like superstars which they also proved during the Olympics. Either they trade their picks for high end roleplayers or they just settle for not winning anymore rings during this current AD/LBJ era. Those guys along with Reaves and Knecht are playing way too many minutes and need help. They have a solid top 4 but desperately need a defensive big to take the load off AD and also need bench help as it's obvious DLo and his bad attitude has already fallen out of favor with Redick.
FWIW I don't believe Flip makes Kessler more "expendable" but I would say that he has more of the offensive skillset they might be looking for in a big. Tough to say but my hunch is they aren't completely sold on Kessler as a long term franchise piece.