Some short notes ..
Some WordPress.com users have started to receive an invitation on the dashboard to try Gutenberg out. This includes me (on my WordPress.com account). Do not take up the offer unless you are prepared to be a guinea pig. WordPress.org users have been receiving the invitation for a number of weeks now.
There is going to be a version 4.9.9 of WordPress which is currently slated for release on November 5th. This will presumably push the date for 5.0 (the Gutenberg release) back. As they originally said (way back) that it would be released sometime in 2018, I guess that there will be some pressure to get it out in December? Who knows!
I get the impression that 4.9.9 is an attempt to clear the decks of any current problems / issues (a) to ease the effort required to implement 5.0 and (b) to minimise any problems that WordPress.org users who choose not to install 5.0 immediately (for whatever reason) may encounter.
WordPress.org users who are happy to install 5.0 when it hits the streets but do not want to use Gutenberg should install the Classic Editor Addon plugin. This can be done now. Consult your developer / support person before taking this step.