Once possession of the Euro ISIS guys is done...Turkey has a card at the table and the EU (especially Germany)...has to play. Failure to play the Turkey poker-game? They will take the ISIS thugs to the coast....launch them on a raft, and land them in Greece.
It might take six weeks for the Greeks to realize who they have and the mess that the EU has to clean up, but I think that Turkey can ask for just about anything from the EU (to hold the ISIS guys), and they will get that ‘wish’.