It is relatively simple. The moment he wants to chase oil club money is the moment his head is not right anymore, and if someone pays an obscene amount he can go.
This can be in 2 years, 4, 8, 10 or whatever he wants.
We should be careful to not expose ourselves so that a player, any player, can fuck us. If he leaves, he needs to fill the club's coffers with hundreds of millions. Anything else, such as him betraying the club, like that Trent loser is unacceptable.
I have no issue for him to be the best paid player in the squad by 2-4m per year. Meaning 2-4m more than Pedri.
He should focus on football and on becoming a club legend. Barca stars retire full of glory and money. Most are remembered as some of the greatest of all time.