One of the new movies is reportedly being written by James Vanderbilt (Independence Day: Resurgence, The Amazing Spider-Man) and will delve into the world of Beast Wars - the Transformers spin-off that features the descendants of Autobots and Decepticons who can morph into animals.
Animated series Beast Wars: Transformers ran from 1996 - 1999 and featured characters like Optimus Primal, Tigatron, Cheetor and Scorponok.
The other script is reportedly being worked on by Joby Harold (King Arthur: Legend of the Sword).
Variety's sources say that one of the upcoming films could be set in 'the Bumblebee universe', while the other would 'revamp' the franchise "with a bigger ensemble and larger production feel".
The Transformers series has pulled in over US$4 billion for Paramount.
Prior to Bay's films, animated The Transformers: The Movie was released in 1986.