Well, it's tough to compare anything to what we are currently seeing in tennis now. I mean you have Federer, Nadal, Djokovic and murray just winning EVERYTHING. Bay far the most dominant era in the history of the game. It will certainly be a while different feeling when these guys are no longer in it as much as they are now, just the fact that the sport will be more open to other players where it has really just been three players winning everything for the last 7 years or so, and will continue to be that way for at least the next three or four.
As far as the next generation, I have to agree there is no real prosperity. Out of all the names you listed, I would say Raonic has a good chance of being top 5 if not better, but the other, highly unlikely. Maybe someone else will come into the picture over the next few years...
5.5. Teaching Pro. Ranked top 10 middle states mens open.