Hopefully not Brett Ratner or Michael Bay.
There should never be more than one director on any given film. Epic Fail waiting to happen.
Also, I'm pretty sure co-directing a film will get you kicked off the Director's Guild, unless you're an established team, like the Coen brothers or something. It happened to Rodriguez when he gave Miller credit for Sin City.
It looks like it will be like this:Tough crowd... Spielberg/Jackson (Tin Tin) get a pass I guess.