Well, if he keeps playing like this, it will be hard to leave him out of the team.
What should be absolutely clear, though, is that Allegri really rates him and intends to use him in the first team whenever possible this season. When you give an 18 year old player his debut in the season opener, a match where Allegri in fact had a lot to lose (it doesn't take many games of bad results at a big club for the fans to get on the coach's back), you obviously trust (and rate) that player alot.
Will definitely not be loaned out or kept rotting on the bench!