At the moment Zimmerman isn't in the 60 man player pool, though of course he could always be added. The other three are. But Akin and Kremer have already been sent to the taxi squad camp in Bowie and Mountcastle will almost certainly join them before Opening Day.
So none of them will start the season in the majors, but yeah I think we will probably see most of them at some point this year. The most likely being Mountcastle.
I've been out of the loop a bit lately. Are we expecting guys like Mountcastle, Akin, Zimmerman, and Kremer to get time on the big league squad this season? Or is the plan to delay their service clock?
If the plan is developing them, I would think playing on the big league roster is better than not playing at all in 2020.