In the long term what that means was not revealed but in the short term it means that Transformers 6 is no longer in the works for what was going to be a 2019 release. In the short term Hasbro is planning a China exclusive animated series in 2019 called "Nesha and the Transformers" while western countries will get "Transformers: Cyberverse" cartoon and toy line that will likely replace the "Transformer: Generations" line that was represented by the Prime Trilogy of toys.
On to the speculating. I am going to go ahead and take "reset" to essentially mean "reboot." In short, the "Bay-verse" will end with Bumblebee: The Movie. The Transformers Writers Room of scripts have probably been trash canned too since they were mostly devised with the Bay-verse in mind. While not saying it, likely the next Transformers movie will not come until 2021 at the earliest to provide breathing room for that "reset" in consumer minds. Any new movies will likely ignore the Bay-verse. For reference, see the various Spider-Man reboots. When the deal between Hasbro and Paramount was renewed, it apparently gave the toy company greater control and say over the movies but since we have not yet seen a movie with Hasbro in greater control of the creative process, we have little to go on for what the result will look like in movie form. All we really have is the various cartoons and IDW comic books from the last decade or so to go by. Those results vary wildly depending on franchise and target audience but the Transformers cartoons over the last few years have hit the "all ages" note fairly well.
