Also as long as making the TFs with CG is really expensive, as long as they're being marketed to the widest possible audience, as long as the movies keep making a brazillion dollars the way they are...
Here is the biggest key factor to why we will NEVER get a blockbuster film that has no humans. Transformers are expensive as hug, unless you want a movie with only two or three period; its going to be too expensive unless its an all CGI movie, in which case then it becomes a 'cartoon' and at which point you lose the interest of at least half the audience it currently has, if not more. Unless its made by Disney, an animated movie is never going to draw in the money and numbers of the franchise as it is currently.
Which is fine, we'd just like decently written humans
(and robots, and dialog, and scenes, and...)