Hello @finkk,
Thanks for asking.
Latest version of X Theme, Pro and Cornerstone is fully compatible with Gutenberg. To find about the version details, please take a look at following page.
Troubleshooting - Version Compatibility KB
This article was last updated on the October 30, 2018. Themeco Products
X Theme: | Latest Supported Version: 6.3.8
Pro: | Latest Supported Version: 2.3.8
Cornerstone: | Latest Supported Version: 3.3.8
X - Content Dock: | Latest Supported Version: 2.0.3 | KB Article
X - Custom 404: | Latest Support Version: 2.0.3 | KB Article
X - Disqus Comments: | Latest Supported Version: 2.0.3 | KB Article
X - Email Forms | Latest Support Version: 2.0.3 | KB Article
…
I also recommend you to please take a look at following article for more details:
Gutenberg FAQ KB
With Gutenberg nearing an official release in WordPress 5.0 we wanted to shed some light on common questions we’ve been seeing as it relates to our products.
As an X or Pro user, what does the Gutenberg release mean for me?
Surprisingly, not much at all. Nothing in the X, Pro, or Cornerstone workflow is changing. If you build your pages with our Content Builder, the only difference is that the “Edit” button to launch the builder is in a different spot. While Gutenberg is replacing the native …
Thanks.