Or how about TF: Beating of the Dead Horse? Seriously, call it TF: Generation 1 and make all us fanboys happy!
Revenge of Megatron...Again. (Because Megatron is one of the big four names in the franchise, there's little doubt he's coming back despite being deader than he was between movie 1 and ROTF)
Transformers: Assigning or Proposing a Title Without Any Idea of the Relevant Plot Details Whatsoever is an Effing ******ed Idea (TF:APTWAIRPDWEFI)
^lol. Well, as mentioned in the above post, we can't say much without a plot, but for possible ideas: 1 - Transformers: The Ultimatum [a movie about Unicron]. 2 - Transformers: The Wrath Of The Tyrant [A movie about Lord Straxus]. 3 - Transformers: The Rise Of The Swarm [A movie about..well, The Swarm]. 4 - Transformers: Ultimate War [A movie about Galvatron]. 5 - Transformers: Age of Blood [A movie about Overlord]. 6 - Transformers: Darkness Within [a movie about a Gary-Oldman voiced Ratbat]. I think I got most of the possible sequel ideas covered.