Yeah, I don't see it either. As much as I wanted Icardi to replace Higuain last summer, that ship has sailed.
Ronaldo can't be the only striker in the box, but IMO he needs a much more mobile player next to him than Icardi. Mario was good most of the year but since he got injured we've seen what a player who doesn't move as much does to our overall play.
Benzema was great with Ronaldo. I believe the right type would be either someone like Suarez or Aguero or Lewandowski who's good on the ball and moves around or someone like Cavani or Kean hopefully who always attacks open space and draws defenders with him and is willing and able to help defensively. Having Icardi and Ronaldo just standing at the center would not be good for us IMO.