I said when he arrived, I think the aim should be getting him to hang around for 8 years, same time Cruyff spent building the modern Barcelona.
If the management can continue to give him what he lacked at Barca and Bayern, support both publicly and privately (I'm sure backing him over the yellow ribbon would have been a good move in that direction) and control over pretty much whatever he wants, then there's no reason for him to fall out with people or get burnt out as he did at Bayern and Barca respectively.
It helps that Italian football is in a shit place at the moment too. If Milan pull themselves together, the ownership situation is sorted out and they put together a solid,City-esque project to get back to the top and topple Juve then they'd be our biggest rivals to keeping him past the contract extension he seems like he'll sign this summer. He's not interested in Ligue 1 or Spain international job.