"Who gets the 'C'?"
If that question is about this upcoming season, the answer is "No one", as they'll roll with three the 3 A's.
If that's about after Landeskog retires (as in, he's forced to accept that he can't play anymore), then it won't be MacKinnon. Guy is obviously a leader, but he's not the type of leader a team needs as a Captain. It would likely be Makar imo....maybe Byram, I guess? People have talked about his ability there, but I don't know anything about that.
The thing is, it can't really be MacKinnon, nor should it be. We all know and have heard stories about his temperment and personality. I don't think he would make a good Captain. He's good to have the "A", but he needs someone like Lando/EJ to keep him in check.