I think, since they killed off Megatron, they should follow the original G1 plot and resurrect him as Galvatron, along with Cyclonus and Scourge and everybody. :P

They should put Galvatron,Unicron,Skywarp,Thundercracker,S­lip­str­eam­,Lu­gnu­t,B­lit­zwi­ng and Blackarachnia,Arachnid.

They need to keep the original characters the third wasn't the same without Megan fox and it defo won't be the same without Shia le beouf