It’s pretty well established that Transformers 4 isn’t really a reboot, as that isn’t needed, but it will feature a new cast and continue the on-going saga of the bots. In an interview with the LA Times, Michael Bay drops some hints as to where the story may be going, and most interestingly he talks about space:

Could the new story involve a departure from Earth? “I think so, yeah, a little,” Bay said. “That feels like the way to go, doesn’t it? I want to go a little off but I don’t want to go too sci-fi. I still want to keep it grounded.That’s what works in these movies, that’s what makes it accessible.”

One word: Unicron. Do it, don’t make him a giant cloud, and the movie will be epic. But then again, I fear what a Bayformer Unicron would look like.