Ronaldo won't steal significant minutes away from Sancho, at least you wouldn't think so. Ronaldo is a poacher now, he doesn't do much running anymore so find it hard to believe he's suddenly going to start rinsing people down the wing as if it was the mid-late 2000s again.
That's one of the differences between current day Ronaldo and Messi. Messi is still the heart and soul of every team he plays for, everything runs through him because his overall game/skill set is still complete. Ronaldo on the other hand has transformed himself into a ridiculously clinical striker/poacher who will often remain uninvolved in a match until he gets his chance and inevitably slots it.