Are they intending to do standalone movies running alongside the 'main' franchise, like the new Star Wars series? Without knowing any better, I'm guessing there will be 'side' movies running alongside/in between Transformers 5 or Transformers 6.

At the very least, there will hopefully be a framework or overarching plot for the next few movies - the movies to date have all been 'episodic', seemingly adding to what's gone before and leaving room for a sequel instead of being serialised/conceived from the start as being part of a series.