SQL Server 2016 is out next year. This will be the fourth version in 6 years; R2 was released in 2010.  Anyways you can get the new Community Technology Preview of Microsoft SQL Server 2016 here.  Be warned though that you must have an Microsoft login, and I know not everyone does.

https://www.microsoft.com/en-us/evalcenter/evaluate-sql-server-2016