He's definitely surpassed Wilander/Edberg/Becker. Becker and Wilander each had one multi-slam year, but Djokovic's multi-slam year was far better than either of theirs. And like Edberg, Djokovic has had two year-end number one finishes, but both of his years (especially 2011) were more dominant than either of Edberg's years at number one. He will quickly overtake Edberg, the only one of the three currently higher than him in weeks at number one. He's one slam short of Wilander, but I can't see him not matching that or surpassing it. He has more Masters than Wilander and Edberg, and the same number as Becker. And I'm sure his overall title count will rise to match the likes of Edber and Becker.
The real question is can he get the career slam and put himself on the same tier as Agassi. Frankly, I think if he won the French this year, I'd put him above Agassi. Agassi was never as dominant or consistent as Djokovic has been. The only thing he really has over him now is the career slam.