If you quote this, remember that I can only speak for myself (and my team), and any timeline I suggest would probably not satisfy every vendor.
To firstly stay within Atlassian’s general time frame, I would expand the time from EAP to GA to at least 3 months. Testing compatibility takes time, especially factoring in the back-and-forth feedback rounds that are bound to come when breaking APIs. In other words, if you aimed for end of September or October, I believe that’s the shortest timeline that would be feasible for my team (though it still feels like a rush). This should also be realistic for Atlassian since it’s in range with what was posted earlier (roughly Q2-Q3). However, it will most likely still not be enough time for very large apps. Like mentioned, vendors have spent 5+ months on Confluence 9 compatibility, and are not yet done.
Secondly, diverting from Atlassian’s time frame, I’d also like it on the record I find the entire Platform 7 launch way too rushed for such breaking and disruptive changes. A more reasonable (and safer) timeline would be to aim for at least one year from P7 EAP to a flexible GA date, instead of today’s roughly less than half-year goal. I would also have liked a coordinated release train between Data Center teams ensuring that none of the platform 7 migrating releases occur at the same time. We offer apps for Jira, Confluence, Bitbucket and Bamboo, and for us it would be best if there is time to release and troubleshoot for only one product at a time, before having to deal with the next one.
In the end, it’s our common customers that will suffer the most from this rush. In addition to their third party plugins breaking and not yet offering compatibility, customers will also experience that their own in-house plugins break down.
Closing thoughts: Atlassian announced in the initial post that Platform 7 is introduced to improve their security posture. Let me tell you what software written in a rush often leads to – Security vulnerabilities.