In response to Matt Mullenweg's comment:

...but we’re not going to push out 5.0 until Gutenberg is something the team working on it and myself agree is ready.

With all due respect (seriously, not sarcastically) neither you nor the team have the ability to truly judge when it is "ready" or not, assuming you do not give it sufficient calendar time and do not confirm it has been used for a significantly large number of use-cases.

This is not a criticism of you (Matt) nor of the team. This is recognition of the limits of human perception and the inability for any one human or small team to envision all the scenarios others will want to use Gutenberg for.

I am concerned about this for two (2) reasons, one of which no one has stated here yet. And the 2nd can be much less of a concern by addressing the 1st.

The 1st issue: It seems that all evidence indicates the team wants to move Gutenberg into core before enough calendar time has passed for it to mature. But this would not be a problem if it were not for backward compatibility, a hallmark of WordPress and one of WordPress' major strengths.

Once Gutenberg lands in core its architecture becomes fixed, warts and all.

How much calendar time do we need? At least one (1) year after vision and feature complete, if not two (2), IMO.

I have lived through many "generations" of computing in my career and seen many sea-change solutions brought to market by over-eager teams that were not ready for prime time. And they all resulted in a significant loss in marketshare.

One such perfect example would be Microsoft's original ASP.NET. They first launched ASP which was a lot like PHP but not nearly as powerful as today's PHP.

But Microsoft envisioned so much more. So they rushed lots of technology and thus they created a huge mess that took them more than a decade to unwind from. AJAX was released after ASP.NET, and it was clearly superior to Microsoft's post-back model. Had Microsoft waiting a while they might have been been able to include AJAX in the original ASP.NET and it would have never needed to be reinvented as it had to be later.

WordPress' original menu system, media modals and customizer all have legacy baggage because IMO they were pushing into core before they had time to mature and thus became fixed for backward compatibility reasons.

What do I proposed as the solution? Include a "beta" Gutenberg plugin shipped with core in WordPress 5.0 to ensure many people try and use it, but also to stop from "setting it in stone" until a large number of people have validated the architecture. AND I would target WordPress 6.0 for Gutenberg's inclusion in core.

If WordPress does this I expect to see all anxiety dissipate, I expect people will start adopting it and the vast majority of users will become excited about it and it becomes clear that it will meet the needs of so many different people. Do not do the above and I predict Gutenberg will be saddled with numerous decisions that cannot be undone and that most everyone will lament for years to come.

The 2nd issue is the React licensing. I believe this will ultimately mean that Gutenburg must be reimplemented in another framework. If WordPress does what I propose for #1 then we will have more than enough time to resolve this issue before it is too late. OTOH, if Gutenberg is included in core in 5.0, chances are we will not resolve it in time and will sorely wish we had.