Actually, there's no one coming through, is there? The Joker and Andy could mop up over the next four years.
Unless you consider Raonic and harrison someone, with a few minor tournaments and already in their 20's, theyre going to be even later bloomers if they get slam success at all.
Andy's mental fortitude and fighting spirit this summer has been extraordinary, he has made about 10 breakthroughs over the last 2 months.
The only place I think any of them can hide is on the clay.
If he plays smart he could be winning slams in his early 30's still.