It'll still be Ronaldo, even more after this world cup than it was before.
If not him, it'll have to be someone from the World Cup winning team. But, a player who can take a good amount of credit for getting his side to win it.
For eg. If Belgium win it, there's no individual performer who's been better than his teammates to have a chance whereas if England win, Harry Kane would have a good shout if he scores 7-8 of all England's goals.
So no one from teams like Uruguay, Brazil, Belgium, Spain will win it since each player on those teams is as important as the next. Though, Griezmann has a chance if France win, he also won the Europa League but his performances are being matched by Mbappe.
If Croatia wins then Modric has a good chance, winning the champions league, always being called the best midfielders in the past 3-4 seasons, as well picking up 3/3 motm for Croatia too I think.