There'll probably be a third, Peter Cullen himself has stated to expect at least two more Transformers films. The transformers I'd like to see are:
Autobots:
Hot Rod/Rodimus Prime - Had quite a main role in the cartoon film, but not the series, so I'd like to see where they could take him.
Kup - Telling all his stories like in the cartoon movie.
Blur - I loved him in the cartoon movie and his quick-talking.
DINOBOTS!
Decepticons:
SOUNDWAVE - I so wished he would've been in the first film. A devart member did a design for him and it looks awesome. (
http://timshinn73.deviantart.com/art/Soundwave-Wallpaper-50216886) and as a bonus we'd get Ravage and Laserbeak!
Skywarp and Thundercracker - The 'seekers' were always around in the cartoon, they should be in the movie, and my theory is because Starscream got away in the 1st film, he'll find those two back on Cybertron, in their Cybertronian forms.
Galvatron - The only logical way I can see Megatron coming back. They better get Leonard Nimoy to voice him like the film.
Shockwave - He was in my PSP game, I want him in the film in his cartoon role as Guardian of Cybertron