If the new crop wants to compete then destroy Federer or Murray and win a title. If they can't beat a 35 year old Federer on grass (well-rested or not) they don't deserve to win a major.
The new crop has some very promising players and the big 4 won't kill them off. The new guys will either be great or they won't.... But it won't have anything to do with the big 4 IMO.