Ronaldo is possibly one of the most driven, self-serving footballers the game has ever seen. If Sane had Ronaldo's attitude he'd be undroppable and end up the best in the world within a couple of years. Ronaldo is absolutely obsessed with winning at all costs, and that's what gives him his edge. There's nowt to suggest Sane will be anywhere near as bloody-minded if his heart is elsewhere. I get the point you're making, but it's a stretch when you're comparing him to a freak one-off.
Edit - fwiw, I think Sane will come back and play the odd game, but it'll be like last season. He'll be a rotation player most likely.