Warner Bros. is certainly not afraid of competition.
The studio has decided to put Sherlock Holmes 2 out on December 16, 2011, which means that it will be opening on the same day as Mission: Impossible IV and Alvin and the Chipmunks 3D.
It's certainly possible that one film may be pushed out of the date due to the extreme amount of competition. While Chipmunks 3D will have family audiences to itself, Holmes 2 and M:I4 will be gunning for the same male, action-loving base. There's no question that they'll hurt each other during the opening weekend.