This writer reshuffling comes in the midst of a producer shake-up. It appears Legendary is attempting to drop producers Dan Lin and Roy Lee.
It's a bunch of typical "industry"-heavy stuff that has nothing to do creatively with the project; if you're interested, read about that here.
Shooting is expected to begin this March on Godzilla under the director of Monsters' helmer Gareth Edwards. Currently, the release date is March 16, 2014.