[shamanNS]

@stumped Nope. It is just Amazon's "Personal Documents Archive" servers that now officially supports epub format as an input format. That is then converted into a proprietary format used by Kindle and that proprietary format is what gets delivered to your Kindle devices and apps.
The conversion "pipeline" has been able to convert epub files for years you only had to jump through couple of hoops / had to game the system by changing file extension from blacklisted ".epub" into something that was whitelisted (txt, png, doc, docx...).

Nothing changed in regards to what format Kindle devices themselves can open natively.