From what I heard the biggest transforming problem they are having is to do with the whole shrinking/growing thing. They are gonna get rid of that as I think Megatron is now going to be a jet.
Frenzy was one of Soundwave tapes, he's the red version of Rumble. He may likely be what people though soundwave would become which is an MP3 player (so equivalent to a tape).
Brawl was a small Jeep in the original series and was a combaticon. They cam together to form Bruticus.
Bonecrusher was a constructicon I think, who formed Devastator. Classic.
Skorpinok, he was a Massive decepticon that was created during the headmasters episodes. In other series he has appeared as a fairly loyal man to megatron. Apparently there will be a major scene with him annihilating an army in the desert.
Might need to do some research for Blackout.
And Ratchet, cmon you should know him. He's the red version of Ironhide and he used to be the medic for the autobots in the original series. Him, Ironhide, Prowl and Brawn get to die heroically at the beginning of the original movie.