Thank you for this. I'm glad this happened.

I still have concerns about how edits are handled, though. I find it odd that any edit - even the most minor ones - can cause a change in the license. I'm not entirely convinced that someone can take a CC BY-SA 2.5 or 3.0 post, fix one spelling mistake, and then release that under CC BY-SA 4.0.

I do hope that you allow a bulk upgrade of the license. Now that the concerns around the licensing have been resolved, I'd like to be able to make all of my content 4.0 and make sure that it is labeled as such.

I would also suggest including the license information outside of the timeline. I think it should be visible on questions and answers, but perhaps it would be ok in the hover text around the attribution would be a good place, similar to how it is in the tooltip for the comment date. Also consider [CC REL in the HTML markup][1] for the page - this does support multiple licenses on the page and may provide hints to search engines and browsers as well.


  [1]: https://labs.creativecommons.org/2011/ccrel-guide/