WordPress 4.9 was scheduled to release on November 14th, 2017. However, due to some issues with shortcodes within widgets (#42548) and changes to the Editor (#42530) during the release preparation, the release date has been delayed by one day.
The new release date has now been targeted for November 15thon Wednesday at 23:00 UTC. It doesn’t serve anybody well to delay things this late in the day, but according to the core development team, it is essential to ensure the late fixes which have landed in the last few days are well tested.
As noted in the 4.9 release delay post on WordPress.org, a final nightly build is now available for testing. It includes three commits – #42548, #42530, and #42545. So, the core development team suggests strongly that you take a look through and test them, and so do we.
So, if you haven’t tested WordPress 4.9, then, now is the time to do so.
If you find any bug or issue, you can post it to the Alpha/Beta area in the Support Forums. If you’re comfortable writing a reproducible bug report, you can file one on WordPress Trac, where you’ll also be able to find a list of known bugs.