Yeah, I agree. Only way MacDonald goes if he's taken as part of a package including something else of value.
That still will make it difficult to integrate the young players, though. Streit, Schultz, and Gudas have spots locked up for the time being. MDZ is an RFA, but he's clearly earned another contract. There's barely enough room for even one of the two lumbering defenders, let alone both of them.
If you keep two of MacDonald/Grossmann/Schenn, that means only one of Gostisbehere/Morin/(Provorov) could make the team out of camp.
Hextall's going to have to be extremely creative and resourceful to juggle this situation. I think that's at least part of the reason why he has minimal desire to take a defender with the #7.