Actually, there is a very simple reason why the toy abdomen looks different from the final movie abdomen. The toy was designed using an earlier concept design, specifically the design immediately preceding the final movie design. This was done because Hasbro and Takara had to start production well before the movie was completed, and the animators had made improvements in the interim.

As for the movie makers using the same animation models for the returning characters, yes, that is proibably what they'll do, but they will also need to modify at least one of them—Bumblebee. His current animation model is based upon the Concept Camaro, not the production model. His RotF alternate form is the final production Camaro, which is slightly different, than the concept design, particularly in the hood and fog lights in the front bumper. Those—the lights in particular—will need to be altered in his animation model.

They have the Optimus Prime and Megatron Leader toys done already & they ARE new. They are BrandNeW molds and theyplan to give the rest of the crew new molds as well. Since they are releasing a Megatron, my guess is he is in the movie. But no confrimation from Bay or Paramount just yet.