First we heard Tim Burton was to direct it, then he wasn't. Then maybe Harry Potter director, David Yates was set to direct. No signature yet. Then we heard Angelina Jolie would play the titular character; no signature yet either. Now a director has been hired, someone you may not have ever heard of.
Robert Stromberg is an Art Director and Special Effects Supervisor with two Oscars (Avatar, Alice in Wonderland). A Maleficent film will of course require his skill set. His resume is very impressive. But does that mean he'll be able to direct a big budget Disney film? I say yes, and a reason why.
Brad Bird came from an animation background to give us the best action movie in years with Mission Impossible: Ghost Protocol. If Bird could successfully direct his first live-action film, why can't Stromberg? I'm looking forward to Jolie (or any actress for that matter) to sign on. Maybe we'll get a chance to see concept art for the film, to get a better sense of the look and tone. All in good time.