The guy won't leave actually, he's getting along very well with team and is getting that 4 million payrise. He's also grateful and, I'd say, even a bit attached to Juventus, you can see it from his interviews, and that's impressive and importante for a 20 years old who came here just a year ago.
I think Conte, the society and the team has handled him very well and helped his growth, and at 20 yo we have already a gem in our hands.
I think in other clubs they would have wasted or limited him, playing him always in his first year and blaming him for some unexperienced performances, but Conte had the intelligence to play him gradually in the first year and now, that he's actually ready, is always playing him. That's the way to do it to develop youngsters at their best, even if they're potential future Ballon d'Or like Pogba.