@22and25 nailed it. Roster limits aren't the issue, the problem for all players over the next few years is the larger pool of eligible players. I think a reasonable estimate would be an average of 3-5 players on every team (all divisions) who would not have been eligible on a normal year. That number will tail off during your son's college years.
IMO, the juco route is no more immune from this issue than four year schools. Lots of guys will get squeezed out of their playing time at D1-3. Many of those guys will transfer to juco. Even worse with juco, they can transfer after the fall semester, displacing guys on juco rosters who thought they had earned starting positions in the fall.
To me the basic objective hasn't changed. Do your best to find a school where you are good enough to earn playing time, regardless of what the recruiter is telling you. Watch their games and judge for yourself (and/or listen to objective, expert advice.) Same is true for 4 year schools and juco.
Those extra covid guys are going to be competing against your son for most of his college years. Don't try to avoid them, just make sure he is competing in the right pool of them.
As far as jucos who move players on, my advice would be to narrow down the list first. The top teams move everyone to the next level, but if those teams aren't realistic for your son that doesn't help him. I think most juco programs vary widely as far as how much priority they put on helping their guys find a good home at a four year school. Once you've compiled a list of possible schools, it will be easier to assess that part of the equation.