Dr. Strange was name dropped in Winter Soldier, so it's going to have to take place after he's already somewhat "established" (the origin told in flashback, somewhat? I dunno...). In that case I can see an older actor taking on the role. Depp would be just fine, but I love the idea of Viggo Mortensen, personally. I'd never thought of Jared Leto as mentioned in that article, but I could totally see that as well.
Not quite sure what is meant by the tone being similar to Iron Man, though. I just don't quite see the Sorcerer Supreme movie being such a straight up action type of show. There has become something of a Marvel movie formula, where they feel a lot alike. That changed with Winter Soldier, which was much more like a spy thriller, and with Dr. Strange they could take it into a whole other arena...not necessarily make it a "horror" movie, but a supernatural type thriller. I think that'd be cool.