You don't rush to give a guy with a horrible track record and zero options a 3 year extension, IMO. I love Gattuso, and I think overall he has done a fine job, but I've always doubted he has any chance of returning Milan to what we once were.
In hindsight, Mirabelli and Fassone wasted a lot of money last summer between Kalinic, Biglia, and Silva. You could argue that Bonucci was also a waste, but the defense has been pretty solid so far this calendar year.
No issue with the three of them going, but if they do, top level personnel needs to be brought in, but I'm not sure how attractive Milan is right now.
In all, we seem as far away as ever from returning to the elite of Europe, and that's pretty depressing.