The review for SE-0264 has concluded. We had a uniformly positive response to the idea of previewing standard library content, but many people had questions and concerns about how the process and versioning was supposed to work. Then @John_McCall advanced the idea of having separately-versioned packages for each proposal. Several people were favorably disposed, and we didn't hear any objections from anyone including the proposers. The core team is, by and large, persuaded that this approach has many advantages and would like to see a revised proposal that includes it.
Thanks to all for your engagement, and for making this process work. Even when a review goes back for revision, we are still making progress, together, on the evolution of Swift.