My opinion;
If you release prior to next season, you don't know who's going to retire.
If many players retire, even filler, then you could be short staffed.
If you are short staffed, then players are pitching or hitting when fatigued.
If fatigued, they are more likely to be injured.
If they are injured, they will not develop, and will probably regress (leaving the injury bug out of this thought)
This could be a scrub, this could be a future star.
My fully stocked, 30 players per level minor leagues is less than $6M. This is barely above 3% of your budget. What are you saving if you cut 4 players per level? Just take care of your minors, you'll thank me later.