Let's get the disclaimer out of the way first: Juventus were a very good team without Cristiano Ronaldo and they will almost certainly be an even better one with him. They are overwhelming favourites to win Serie A and, while the Champions League -- like all knockout competitions -- is tricky to predict, they have to be among the favourites to win that too.
The question, though, is how much better they will be and, crucially, what manager Max Allegri -- with the collaboration of Ronaldo and others -- can do to get them to maximise potential. In other words, you got yourself a CR7 unit (or, more accurately THE CR7 unit.