Hasbro said they were going to release more toy info on the release date of the movie, to avoid spoilers I spose, which I'd be guessing would include the new characters Wheeljack, Mirage (Dino) and Soundwave (as a car).
That would pretty much cover all the convertible cast.

I can see an eventual release of an Optimus toy with a dozen odd weapon attachments, like in his mobile armoury (trailer)... maybe even something like the JP THS figures with plugin attachments.
That I would buy.