SQL Server 2019 was announced recently, a preview version is now available.
SQL Server 2019 CTP 2.0

There’s also a preview edition of SSMS, version 18.0, that will work with SQL Server 2019.
SSMS 18.0

Brent Ozar has a short article listing items removed in SSMS 18. Database diagrams and T-SQL debugging are two of the big features removed.

Aaron Bertrand has a good article summarizing the new features on MSSQLTips

A more in depth overview of the available features in a Microsoft white paper (registration required).

A small change, but one I’m excited about, is notification of the column involved when getting the ‘string or binary data would be truncated’ error. John Sterrett has an article on this feature.