This year the NFL Draft advisory board changed their policies by only telling players if they are rated as a first, second, or third rounder. Before they would tell players if they were considered an undrafted draft pick, but that has changed.
If you are anything later than a fourth rounder they are telling you to return to college. Some will listen to agents over the advisory board, but it could hurt the player.
As you can see the numbers are already down. It will be interesting to see if more underclassmen enter the draft than last season. I cannot see it, but who knows.