Yes but instead of "writing" a new Transformers film overnight which is apparently what happened on the last two - Cameron worked on
the idea for Avatar in the 12 years since he finished Titanic.
He actually waited 12 years to make it so the technology would exist to make it the way he envisioned it.
He originally wanted to make it right after Titanic but waited 12 years for the tech to catch up.
Can't really see Michael Bay waiting 12 years between Bayformers movies in order to make an action film.
You can say what you want but I loved Avatar . It was just an entertaining ride from start to finish and James Cameron is one of my favourite directors for that genre.