We evaluated Gutenberg and also took some inspiration from it when developing the Volto page composition editor.
Gutenberg is pretty neat. Though, it targets advanced technical users that know basic HTML and CSS (at least how it works). You can configure anything you could imagine and that's indeed pretty impressive.
Though, the main use case for Plone is large organisations with lots of editors that do not necessarily posses in-depth technical knowledge. Because of its flexibility, Gutenberg would require lots of editor training, which is a big cost factor for large organisations. Therefore we decided against integrating Gutenberg and we are trying hard to make the Volto page editor as user friendly as possible. Gutenberg is the perfect editor for Wordpress and its main target group: agencies that want to build websites with limited in-depth technical knowledge.
It would be a living hell in Plone if you allow thousands of editors the freedom that Gutenberg gives the user. No way to make sure you have a consistent corporate design, accessibility, same look-and-feel, etc. If you look at university websites or larger websites, you will see what I mean if you look at a site that allows the user even too much flexility in TinyMCE or CKeditor.
My personal advice would be. If you want Gutenberg, use Wordpress. The target groups of Wordpress and Plone are just too different IMHO. You will never end up with a system that satisfies your need.
From a technical standpoint:
Since Gutenberg it is written in React, integrating it into Volto shouldn't be too hard and easier than integrating it into classic Plone.
Though, for Volto we decided to go with DraftJS instead of Gutenberg because of the reasons outlined above as well as the fact that the main work is actually the integration of the editor into the CMS (how to display blocks on the rendering, content browser, resolveuid, etc). Making Gutenberg working in any system is easy and doable in a day or so I guess. Though, then the real work begins...