I know it's a little early to say this, but if they make a third one, it would be interesting to see these characters in there. Alpha Trion could be one of the first 13 Transformers who will guide the Autobots to defeating Unicron and can explain how he and the rest of the first Transformers defeated and trapped the Fallen on Earth (they might actually do this in the second if they have him there). The Quintessons could try to take over Cybertron as they tried in G1. Primus & Unicron can be there to explain how Cybertron and the AllSpark was made and expalin how Unicron fell to the dark side. What do you think guys? You can input more ideas if you want.