Why would the Australian Open matter? He is already regarded as the best in his sport by most of his peers, present and past. Many players are playing longer nowadays due to advances in sports science, clever scheduling (take note Nadal) and racket technology. Though the modern game negates longetivity due to the long rallies.
The greatest sportsman ever is such a subjective term, close to impossible to say. Unless someone comes along and has a McEnroe (84), Federer (2006), Djokovic (2011) year after year for a long ass time. Federer had some great years, though Nadal impeded that to a certain degree on Clay during Federers prime (2004-7).