It’s going to be a big year for many clients. If you have servers running Windows 2008 R2, you’ll be needing to upgrade before security updates cease in January 2020.
Some gotchas… this is likely not a straight OS upgrade for many. Server 2019 may require hardware upgrades to add additional resources to your physical systems. This may be a good time to look into a complete server upgrade as opposed to putting time, energy and $$$ into a server you will need to replace in a year anyway.
Check out the Microsoft announcement:
https://www.microsoft.com/en-us/cloud-platform/windows-server-2008