Last week Microsoft Exchange Server team announced at Ignite 2017 that Exchange Server 2019 will be released near the end of 2018.
Exchange Server 2019
The next version will be called Exchange Server 2019 and it will be an on-premises version.
Currently, there are no details about the architecture, Roles, Requirements etc but the first preview will be available during mid-2018.
The final release will be available at the end of 2018 like Exchange Server 2016 that was released on 31 October 2015.
We will keep you updates with more details once we have them.