With the final week of filming (giving them 14 months to do post production - not sure why the movie was pushed back in the first place), it looks like some blue-screen filming is now taking place, as well as word that there will only be four robots in this movie.
It has also been noted that Steve Jablonsky (who has done the music for the previous Transformers movies), is not likely to be available for this one... but I don't know if that is based on the original June release, or the delayed December release, and if he is busy for the entire year or just the first half.