3.5 weeks feels awfully short to go from beta to production on a change so big. Isn't Gutenberg going to be the new default, no opt-out? Kind of makes me nervous.
Beautiful! Also, that makes perfect sense. Thank you for the link!
There's also this plugin which removes all other references to Gutenberg so if you're building sites for clients they aren't able to accidentally switch the classic editor off, and don't get nag screens about trying Gutenberg. https://wordpress.org/plugins/classic-editor-addon/
There's been a stand alone plugin activating the Gutenberg editor out for ages now. You can install it and test how things work right now in 4.9.8 or whatever version you're running.
So this 3.5 weeks thing is a bit of a distraction.