Hello smacktoward! I'm thrilled you currently make your living on top of WordPress, and hope you can continue to for many decades to come.

"Automattic Automattic Automattic Automattic Automattic" Throughout your comment you attribute a lot to Automattic that is really core, or contributors, or me. There are hundreds of contributors to WordPress (and Gutenberg) that don't have any association with Automattic, and it's not fair to them to attribute anything good or bad about WordPress to a single company.

"I don't think [...] has handled communicating it very well" That's totally fair, and I believe we can always do a better job communicating. We've done a lot, such as with wordpress.org/gutenberg, the messaging in 4.9.8, at pretty much every WordCamp this year, and my big annual addresses the past two years, but we're not reaching everyone. Web hosts and agencies are helping a ton here to educate their customers and clients, and it's very much appreciated.

"It seems reasonable to expect lots of themes and plugins will break when it goes live, especially older ones that haven't been as actively maintained." This is why we have done a wide public release of the beta plugin and it's active on over 600,000 sites now — this is the most widely tested feature ever to come into core. People are running it with every possible combination of other plugins, themes, and hosting environments, and we've been learning a ton and fixing as much as possible beforehand. I don't claim any software is perfect, but this code has had more testers than we ever get for a beta version of WordPress, which is usually just a few thousand.

"My suspicion, even though [...] has denied it strenuously, is that the master plan is to slowly phase out PHP and turn WordPress into a React-only project." There are no secrets, on stage in 2015 I asked all WordPress developers to "Learn Javascript Deeply" because Javascript interfaces talking to REST APIs was the future of the platform. This is how the Customizer has worked for years, but you're correct that Gutenberg is the first major, full feature to be built on our own REST API and does use React. (In fact we were part of getting Facebook to remove the patent clause from React, which paved its adoption in the WP community and with many others.) So you're correct it's part of the master plan, but not that it has been denied at all. There will always be some PHP for the server side of things, but Javascript is the way forward for the interface and wp-admin.

"If the plan really is for WP to become a React project, a whole lot of PHP developers are going to need to become React developers in relatively short order. Some will be able to make that transition, but I worry that many will not." I'm concerned about this too, which is why I've been advocating for PHP-only developers to learn Javascript for 3 years now.

"The more I learn about Gutenberg, the more I wish [...] had just started a second, React-based project and used that as a clean sheet of paper, rather than taking all these ideas and trying to jam them into WordPress to make some sort of software turducken." First, I love turducken. :) But also, the WYSIWYG was in Javascript before, so it's not like editor-modifying requires a new language you didn't know before. The PHP metabox API still works just like before, and we and others are creating tools that allow PHP developers to interact with Gutenberg. But I'll repeat again that if someone wants to be a relevant web developer in a decade I don't think you can be PHP-only, and you should begin learning and mastering Javascript as soon as possible.