LEGO has been obtaining much license such as recent movies figures even like The Lone Ranger. At the rate it is going, it will not be long we expect to see more possibility of LEGO doing other stuff.
Fans of LEGO has done these He-man and it provided a great concept of what LEGO He-man will be. Only missing Battlecat and Hodak. :P
Will it come true one day? Well Mattel would need to release the license I guess. We never know but it is one good concept I must agree and I can see the possibility of Castle Grey-skull in LEGO.
In fact some fans already did that!
More at his Flickr