You know that those would be the first toys released.
Aside from the faces, the bodies of those two characters are almost 1:1 with the movie models so there is no point in redesigning a whole new figure when there are already a dozen releases for each. All that it needs is a 'Frankenstainy' Animated type head on an existing ROTF figure and that's it to get a pretty accurate TF:Prime character representation.
With Arcee they could use the TF1 Arcee mold but with Bulkhead and Ratchet, they would need new molds if Hasbro wishes to go that far.
With the Decepticons, a Movie Megatron with a new head would do but new molds would be needed for Soundwave and Starscream.