I'm reserving criticism until I see more of the story in future trailers, thought this does seem like a cynical move to capture a built in audience with tarted up CGI (please no Phantom Menace jokes).
Here's what I find intriguing: we know that the Wizard is not a real wizard at all, but a humbug. In the Wizard of Oz, he promised to grant wishes but never actually delivered on any of them. In this movie, this humbug finds himself in the magical land, but this time he actually has to DO SOMETHING in order to help the people, even though he is not actually great and powerful.
I like stories about Messiahs you don't expect, because that is how it was with Jesus. He was the Messiah, but the kind that they were hoping for.
I'm hoping for this movie to develop that theme and make it fun to watch.