That's a big jump across the two biggest changes to Server in many years:
1) Hyper replaces TDE
- some extract data may change in small ways, lots of testing
- developers will have to use 10.5+ to edit workbooks with Server-refreshed extracts
2) TSM replaces tabadmin
- any admin scripts you run on your Windows server will need to change from tabadmin to tsm
2018.3 doesn't exist in production. How do you know it will becoming in September?