Hurt pro leagues, the nfl in particular? My initial thought are that all the best players going to a handful of teams, and the rest fizzling out means far less developed talent, and less talent overall making it to the NFL. If the player pool to choose from diminishes, then the number of quality players goes down, thus hurting the NFL, which will adversely effect CFB.
What about setting up a D-league that pays players slightly better than the college experience? This league also bypasses the 2-3 years out of HS requirement.