Taken from Joblo.com this is what the story will be for He-Man.
“Prince Adam (Tatum), son of King Randor of Eternia. When the King is overthrown by his trusted advisor Skeletor, Prince Adam is cast off to the wastelands of the planet along with his sister Adora, his mentor Duncan, and his childhood friend Teela. Together, the siblings encounter a mythical sorceress who shows them the power of Castle Greyskull, the mystical center of the planet. With the Sword of Power, Adam will become He-Man, the Master of the Universe! That's right people, Adora! That means that not only will MASTERS OF THE UNIVERSE 3D feature He-Man, but She-Ra as well!”
Masters of the Universe will be directed by Jon M. Chu of Step Up 2, 3 and G.I. Joe Retaliation fame.
Let's not also forget that Tatum will also be playing Gambit, who just so happens to be my favourite X-Man, so mess it up Channing and I will find you!