The new ADG 3 experience is on its way to Confluence Cloud, so we'll shortly be enabling ADG 3 for developers who have opted in to be part of the Confluence Cloud vendor beta. If you haven't yet opted in for this beta, you can do so here: https://goo.gl/0RzTVH
For a rundown of the changes that can be expected with ADG 3 on Confluence Cloud, have a look at this page: https://confluence.atlassian.com/x/-i6LN.
As stated on the above page, customer sites with add-ons installed will not have ADG 3 enabled for now. Additionally, if a customer with ADG 3 enabled installs an add-on, they will be reverted to the previous user experience. We're essentially looking to fix some key issues affecting add-ons before removing this exclusion. These key issues include, but are not limited to:
- Moving web-item locations into the global sidebar (system.header/left has already been moved)
- Resolving blocker issues relating to theming & custom content
- Resolving blocker issues relating to add-ons settings screens
Should you notice issues relating to your add-on with ADG 3 enabled, please create a CE issue, and attach the "Navigation - Single Page App" component to it: https://ecosystem.atlassian.net/projects/CE/issues