Could be - but Holm was bad in only 1 year, his first in NA. I wouldn't give up on him without giving him 1 more year to progress.
I wouldn't be so sure Milic is ready to step right in to AHL level competition. If he is excelling in the ECHL and Holm is not excelling with the Moose, they can be swapped at any time. Players don't need to be waived from the AHL to the ECHL AFAIK.
Really, we have 2 pro goalies right now, Holm and Salminen. That's it. There is plenty of room. Well, now we have 1. That is assuming Helle is moved. If he stays we have 2. Still plenty of room.