I don't think he will. He'll be playing with world class players and in a system that will take his game to the next level. He won't flop. He's an incredibly talented player.
I see many think he'll play on the left wing, but I see him playing more in midfield in a rotation with KDB and Gundo. No doubt he'll play wide occasionally though.
I also see concerns around Jack's shin problems, well given City play in excess of 50 games a season and have a very good squad there is no need for him to play in every fixture (which he won't) so he'll get decent breaks to keep him fit.
Spend the 100 million wisely. Don't be like Spurs/Bale.