In reply to Tammie Lister.

I am not speaking for Matt, I am speaking as someone involved in the project. My comment comes from both the roadmap:
https://make.wordpress.org/core/2017/08/11/revised-suggested-roadmap-for-gutenberg-and-customization/

Matt also says the following in the most recent post:

That post won't be published, and instead I'm here to say that the Gutenberg team is going to take a step back and rewrite Gutenberg using a different library. It will likely delay Gutenberg at least a few weeks, and may push the release into next year.