I've mentioned this before but I tend to think of the quartet of big bats at Iowa that two will stick around and get folded into the big league team. I also think, all else being equal, they'll keep one righty and one lefty, and one IFer and one OFer. So Long+Caissie or Alcantara+Ballesteros.
Their further performance will obviously impact the decision, and I think the Kyle Tucker situation will impact things (i.e. if he sticks around you can feel a little more comfortable trading both of Alcantara/Caissie), but that's my default assumption at the moment.
I also don't think there's a lot of daylight between Mo and Caissie/Alcantara. And if you assured me he wouldn't be able to catch he'd still be behind both of them.