AS explained in a blog post yesterday, Microsoft is now going to make 2 major releases per year, 1 in April and 1 in October.
We are transforming how we do service updates for Dynamics 365 (online). We will deliver two major releases per year – April and October – offering new capabilities and functionality. These updates will be backward compatible so your apps and customizations will continue to work post update. New features with major, disruptive changes to the user experience are off by default. This means administrators will be able to first test before enabling these features for their organization.
In addition to the two major updates, they will continue to deploy regular performance and reliability improvement updates throughout the year. Also, release notes will be published months prior to each major update to help you plan for the new capabilities. The release notes for the October 2018 update will be published on July 23.
Starting with the April 2019 update, you can validate major updates in a sandbox environment in advance of the update release. This will help you assess productivity and efficiency gains of the new capabilities, as well as train your end users about new capabilities. We will publish the timeline of when to expect updates in sandbox environments in advance.