In reply to Tim.

@Tim - Honestly, I think it's a mistake to flat out replace TinyMCE with Gutenberg. Users/Developers need to be given the choice which one they want to use.

I liken it to Microsoft's huge mistake with forcing the Metro UI onto people with Windows 8 without offering them the choice to use Aero (Windows 7's interface). As a result, Windows 8 adoption after 12 months was a hair short of 50% of Windows 7.

When you force such a fundamental change on people, you risk them re-evaluating their options. They may either opt to not upgrade WordPress or move to a different solution.