I noticed retention policy is a new feature coming in 2.0.2.10 which is in canary now. Given how important that is to me, I was wondering how long it generally takes for such canary releases to move to stable.
Unfortunately, there is no set release schedule for Duplicati. A GitHub milestone for 2.0 stable has been created, but to date only 1 item has been closed. 
However, you can help speed things up by submitting your own code for any of those items or, if you’re not a coder, donating to Bounty for the items you want to see implemented first (Sia support is a great example of that).