Once Dec. 31st hits they have to have a final team roster of 20 players for districts and Nationals if the team was to make it that far.
I think what the OP is trying to say is someone on the 21 player team is going to get cut Dec. 31st, which is BS since there are still roughly 2 months left in the season.
Not sure how BB is planning to compensate the player who is cut at the end of December with roughly 1 1/2 months worth of the season remaining.
OP doesn’t say if the new player is a forward or defenseman, but that would suck for any of the current players knowing someone isn’t going to be with the team beyond December.
Of course, players get hurt and this could be a non problem if several players are out with extended injuries.
I personally would address the situation now, before the season starts.