http://comicbookresources.com/columns/?column=13
"Transformers 2" is being prepped for 2009, as is a new cartoon series to spin off the upcoming movie.
The reason given to licensors as to why the robots look so different in the film is so that hardcore fans will stay loyal and keep buying the old toys, which they're relaunching, even if they hate the new movie.
Licensing has explicitly stated that companies doing merchandising have to avoid doing anything too similar to the original Transformers line, so as not to mix the two separate and profitable properties.