Depp has the look for the role. And he's well connected with Disney. But I think my reservations about him are the same as Bill's. Johnny Depp seems to inject this air of camp into almost any project he's involved in these days.
I know there was a lot of talk about Joaquin Phoenix playing the part. What I also heard there was that he was interested, but also concerned about the amount of CGI the project would require. And evidently his concerns are that he feels more of a need for practical effects that he could interact with as an actor. I know that Ewan McGregor expressed similar concerns about the production of the PT, so I don't think it's an insignificant consideration.
Ethan Hawke seems like an interesting choice. He can pull off the look. As for the character? I honestly don't know enough about Dr. Strange to say one way or the other.