After pushing back the release date of WordPress 5 from 27th November to an unannounced date, the new release date has, early hours of today, been announced as Thursday 6th December 2018.
This is a very soon date which gives people little time to plan.
From feedback on the announcement page, it appears the majority think the date is driven by the WordCamp US conference. An event should never be the driver for software release; the driver should be that the software is ready and Gutenberg appears not to be ready.
You can edit your wp-config file to prevent an upgrade (if you host your own site) or can install the Classic Editor to get the old functionality back.