[bradwestness]

I don't understand the point of what he's proposing. Rewriting WordPress as completely as he wants and breaking all existing plugins and themes would surely just result in someone forking the existing code and maintaining a backwards-compatible version.

The ecosystem is the valuable thing, and they'd be insane to throw that away. All the problems he notes are basically just a result of WordPress growing and changing over the decade it's been around, and/or direct results of having originally been written in PHP 4.

Gradual refactoring, as you say, makes more sense. Otherwise you might as well just build an entirely new system from scratch.