I would panic a little bit. Coaches are human and they want to bring in their guys. I have seen it at a few levels but it isn't always the case. If your kid is a big time player he probably won't be affected but if he is a borderline starter it may be time to go to a team that wants him.
I don't think I would panic. Be concerned? Yes.
At my son's JuCo, the administration didn't have a replacement until mid-July. With students reporting to campus in 30 days, he really didn't have time to scout and sign players. He had to deal with buying/renting a home, arrange movers, etc - no way he had time to scout and sign any players. He had been an assistant coach at a D1 university that was out of the area. The incoming coach had to work with the returning players and one's that had already committed to the school. The next year he was able to recruit "his" players.