I think Roger Federer is going to be number one again. The reason I say that is because his game is sustainable in the sense that he is not only very talented, but there is not much about his game that is forced.
So he doesn't get injured that easily. If he just plays the minimum amount of tournaments, maybe two or three more, I think he will be number one again and win Wimbledon two more times. Plus one or two other grand slams.
Check out this article about why Federer and Serena Williams have been able to have such long careers!
