There's a Transformers cinematic universe being built right now by Paramount, which like every other studio is taking its cues from Marvel's Avengers. To achieve that goal a "writer's room" was formed and came up with ideas all the way through 2025, including prequels, sequels, and spinoffs featuring the Autobots and Decepticons. The multi-billion dollar franchise's fifth film has long been set to arrive some time in 2017, but now Paramount has confirmed its expected summer release date, and gone a few steps further by announcing what will come next.
Paramount has confirmed the Michael Bay-directed Transformers 5 for June 23rd 2017, which would have Optimus Prime going toe-to-toe with Wonder Woman. Don't be surprised if something gets moved to avoid that tangle. Transformers 6 will then arrive a year later on June 8th 2018, then Transformers 7 on June 28th 2019.
This is expected to be Bay's final Transformers movie but, to be fair, he's been saying that for years and can never turn down that fat paycheck. So we'll see. It's telling that Paramount has slotted the sequels only a year apart, though, which suggests they may have directors already in mind who can get the production going quickly and efficiently.