I don't think we will see many changes in defence and midfield from this point. Judging by Allegri's interview few days back, he seems satisfied with midfielders he has now and he will give space to youngsters also, especially in the American tour. To see what they're made off. Also it's almost impossible to get rid of some players like Sandro, Arthur and Rabiot. They have fat paycheks they wont get anywhere else. Without getting rid of deadwood, no one will come.
But it's quite obvious that we are short in the attacking department and this is where we'll se most action from now on IMO. Seems to me that player like Kostic is a back-up plan for us at this point and that we are cooking something much better.