As you may know (otherwise, this is it, you know Winking smile), SQL Server 2008/2008 R2 is going out of support in July 2019 (https://support.microsoft.com/en-us/lifecycle/search/14917), while Windows Server 2008 is going to be out of support in January 2020 (https://support.microsoft.com/en-us/lifecycle/search/12925).

To help you migrate your workloads still running on these systems, Microsoft is extending the security updates support for 3 years when running these systems on Microsoft Azure.

That said, it does not mean you can seat back and relax during these 3 additional years. If you have to enjoy this offer, this means you were not already ready for this end of support date. So, enjoy these 3 more years in Azure BUT plan your migration from these systems.