As for a "legend", I think what he did last year only is enough for that ... and you can go until the final of the Australian open 2012. And that includes all of his wins against Nadal.
McEnroe's 1984 was enough to make him a legend.
It's the same for Djokovic.
Wilander's 1988 had 3 slam wins, which is a great memory for many people, but not that level. Also his Australian open and French open wins were not that memorable. The US Open was the most memorable with his win over Lendl.
I could agree with your first 2 points, but Murray 'in Edberg, Becker, Wilander category' please, do no think so. and this is coming from someone who dearly likes Murray.
Yet I've watched the whole carreer of these players, and I do think Murray is in the same category
He has been unlucky facing such 3 competitors and he's still very young. I still believe he can pull a "Wilander-year" one day