Yeah, but which young talent is going to be ready in the next 3 years? Raonic, Nishikori and Dimitrov aren't young talent; they're in their prime. Nishikori might snatch some time at no.1, but I doubt it. Kyrgios and Coric might just about be ready before 3 years is up, but it'd be a stretch.
I think all the guys that are 18-19-20 years old today and are ranked between 50th and 200th in the world can explode in the next two years. It's difficult to know exactly who, because at this point it's not enough to see them play, it's partly up to their future choices, their capacity to adapt to the Tour, their training programs, their physical evolution (the Zverev height discussion a few posts ago was a good example), etc. To sum up : things that we can't predict. But the sheer number of promising young players who already managed to beat seasoned top 100 players is something we haven't seen in a long time, so I'd be surprised to see the same guys at the top in two-three years.