That being the case, I can see a well-prepared, well-publicized and well-maintained fork easily taking the cake from WP.org in the near future, as WP.com becomes more like the SquareSpace they admire so much.
Purely anecdotal, but from a hiring stand point, it's extremely difficult to find good software engineers that are willing to work on or maintain a Wordpress-based project even as part of their duties. No one seems to want to touch it. I have yet to come across any engineer that would classify Wordpress as a resounding success in their eyes.
However as you see in some other comments on this thread, backwards compatibility has been key to WP's adoption which can make it challenging to fully iterate the user and developer experience. With Gutenberg we're doing this, and it has generated a huge amount of pushback and even conspiracy theories. Hopefully in a year or two we'll look back at this as something we're not sure why there was even an issue.
The last time people threatened or actually forked WordPress like this was when we first adopted WYSIWYG in version 2.0, in 2005. Part of why WordPress today has 10x the market share of the runner-up is because we think a lot about these decisions, listen to tons of feedback, but are willing to occasionally choose controversial-at-the-time decisions that turn out right in the grand arc of things.
What's going to happen with the entire plugin ecosystem? Say I'm a plugin developer - am I going to jump ship to an untested fork with no company backing it, or am I going to go with a safe bet?
I'm happy to see a fork of Wordpress if that's the itch that people want to scratch (more power to them!) but the value of the app isn't in the code itself, is it?
This model has proven successful before in other projects faced with similar issues