SQL Server 2016 mainstream support is scheduled to end 7/13/2021 as defined by the lifecycle policy.
With the crossover to extended support, Microsoft is committed to providing a final service pack for SQL Server 2016 to all customers. The release of SQL Server 2016 Service Pack 3 will be shipped after mainstream supports ends, targeting September 2021. This will be the final service pack for SQL Server 2016.
For any questions, please work with our support channels as documented in our help and feedback page.