Much as I like Brett Dalton on this show, he was a large focus of the last few major arcs regarding HYDRA, and now he's Hive. Having him get another arc focused on another transformation for him -right- after the Hive thing seems like too much.
I doubt it will be Daisy. (SHIELD is pretty much the Coulson and Daisy show.) If Mack goes, that's going to lead to some revolving door jokes for a certain kind of character on the show.
My guess is Lincoln. He's had some build up, but he's not too central to anything, and his major connection to SHIELD has gone rogue.