That looks nothing like Leonardo. The one chalk face portrait of his that he did shows a fraZZLED bearded and wrinkled face whose nose cannot be mistaken for that of the Mon Lisa.
Secondly, there has been no mention of this in the literature that was contemporary to that period. I would think contemporaries like Michelangelo, Raphael, Donatello etc would have noticed this resemblance and commented on it.
http://www.bobbyseale.com/bptop.JPG