SQL Server 2016 RTM version has been released and available to download from 1st of June. You may download the ISO from TechNet Evaluation Center, MSDN Subscriber Downloads, Visual Studio Dev Essentials, or your own Volume License server(s).
For more details on the product you may refer the announcement from SQL Server blog here and Channel9 Video on the release here
SQL Server 2016 Datasheet
Download detailed information about licensing SQL Server 2016