Transformers 5 (the official subtitle TBA) will begin production this summer under the direction of Michael Bay and may, in fact, end up being the last Transformers installment that Bay oversees as director. In the meantime, Paramount Pictures shall be moving full speed ahead with plans to assemble a Transformers shared cinematic universe, complete with a spinoff centered around Autobot Bumblebee (set to arrive in 2018) and then Transformers 6 in 2019. Three new Transformers movies in as many years might seem excessive, but seeing as the first four movies in the series grossed over $3.7 billion worldwide it's not difficult to understand Paramount's logic here.
While the four live-action Transformers films released to date have indeed all been massive commercial success, they were nonetheless rather expensive to make (with the most recent installment, Transformers: Age of Extinction, having a production budget of $210 million). Paramount will get some help with covering the costs of Transformers 5 from the state of Michigan, as the next installment will partly film in Detroit this summer - in turn, receiving an incentive that comes from agreements reached before the Michigan state legislature ended incentives for filming in the state, back in July 2015.
This news confirms previous reports linked to a Transformers 5 casting call that claimed the movie will film in London and Detroit, starting this summer. Here is the statement from Paramount Pictures president of physical production Lee Rosenthal, regarding the $21 million incentive that Transformers 5 will receive from the state of Michigan (per Variety):
“Michigan has been so welcoming of Michael Bay and the ‘Transformers’ movies over the years and we are thrilled to be returning for this next incredible installment."
Transformers (2007) and Transforms: Dark of the Moon partly filmed in Michigan, while production on Age of Extinction likewise took place in Detroit specifically, among other cities in the same state. The return to a major shooting location from Age of Extinction in Transformers 5 makes all the more sense, seeing as the latter will carry over both the story threads and main characters from Age of Extinction in particular. So far, Mark Wahlberg is set to return in Transformers 5 as inventor/mechanic Cade Yeager from Age of Extinction, though it's not known yet if Nicola Peltz and Jack Reynor will also reprise their roles as Cade's daughter Tessa and her boyfriend Shane, respectively. Nor, for that matter, is it clear yet why Optimus Prime will re-enter the picture in Transformers 5, after having left Earth to find the Creators in Age of Extinction.
However, as part of its initiative to (pardon the wording) transform the Transformers franchise into a cinematic universe, Paramount will reportedly be taking a more inter-connected storytelling approach to future installments in the film series. As such, Transformers 5 screenwriters Ken Nolan (Black Hawk Down) and writing duo Art Marcum and Matt Holloway (Iron Man) - all members of the Transformers writing group that Paramount put together to plan out the Transformers cinematic universe in 2015 - will be plotting the seeds for developments in Transformers 6, as well as (potentially) the Bumblebee spinoff - and maybe even the animated movie spinoff revolving around the Transformers' home planet Cybertron, which is said to be in development too.
Transformers 5 will open in U.S. theaters on June 23rd, 2017, followed by the Bumblebee spinoff on June 8th, 2018, and Transformers 6 on June 28th, 2019.