It should be common knowledge at this point that there is one non-backwards compatible leap between our version history with concrete5. For about 5 years you could just hit update and migrate from version 5.1 to 5.2 to 5.3, etc all the way through 5.6.x.
We then released "Version 7" which was a pretty deep rewrite of code to follow modern PHP standards. We built migration tools, but it really was a process of building a new site and pulling old content into it. Since those days we've dumped the leading "5." from our version number, and we've been good about keeping that magic update button working. We hope to never have to release a non-backwards compatible version again.
All of this action happened back in 2014/2015. At the time we promised that we would continue to support version 6, from a security standpoint, until further notice. We additionally promised that when that notice came, it'd be a year out. We totally understand that there are important sites still built with version 6 and it takes time to come up with a coherent strategy to rebuild your site. We know you need warning so you can plan, so we appreciate the importance of giving you a clear day to start a clear countdown.
So today is that magic day.
We are officially announcing end of life on version 6. If we are made aware of a major security issue we will still collaborate on releasing a fix for the next 12 months. After 8/24/2019 we will not support version 6 at all.
You may have noticed all our own version 6 add-ons were made free some time ago. As it doesn't make sense to sell extensions for a product we don't support, we will be disabling the legacy marketplace sales in 3 months on 11/22/2018. Support will continue to function on those listings for 90 days, after which point the old marketplace will be removed entirely.
Really it has been well over 3 years since we left this version behind gang. We're already working on version 9 of concrete5. We've got big things ahead and while we know there's plenty of work to do, that work needs to be focused on the future.