Microsoft Dynamics 365 Finance & Operations will have a major version 10.0 released during the next two (2) weeks. Based on the D365 F&O procedures rolled out during 2018 Q3, the D365 on-cloud customers are to be on the latest three versions, and that would be versions 10.0, 8.1.3 and 8.1.2. Customers on the prior versions like 8.0 & 7.3 will need to update to one of the supported versions.
Microsoft has streamlined the release management to two major releases per year, in April and October of each year. This has made the update needs predictable and the customers are able to plan better.