Even though TF5 put the brakes on the live action movies, the producer Lorenzo di Bonaventura has commented that it made enough money to warrant more... but they are currently focussing on the Bumblebee movie at the moment, but will look for script writers for the next movie, soon.
The source article can be found here, and we are likely to hear more about it this weekend at SDCC, as there is going to be a Bumblebee Movie panel.