People are thinking slams grow on trees. Novak has only got 6 slams in 7/8 years on tour. At the moment, even if Nadal wins no slams, he will have to double his slam tally to surpass Nadal. Not an as easy a feat many are making it out to be.
Oh come on, you know you need some years to grow and mature before raking up slams, he's playing at his peak now and has won 5 slams in two years. But he's just 25. What makes you think he won't win many more slams in the next 3-4 years?
Plus it's not like the other players in the Top 15 are younger than him, quite the contrary.