Transformers 2 writer Roberto Orci has posted on the Don Murphy’s message board that there is the possibility of there being ten robots on both the Autobots and Decepticons sides. He also mentions that some of the Transformers won’t be at the forefront and will only play a supporting role.
Hopefully, with all the characters, we can expect to see some discussion between these groups of bots, and with not all of them being key to the story, some good characterisation can be made.