I should note that the existing hooks will not work with the new editor at this time as the plugin has not yet been integrated with them. That hook, though, (as well as those @Simone mentioned) is going to be the presumed path for integrating 3rd party functionality. I anticipate we’ll be able to leverage all the existing tiny-related hooks for the actual releases.
Reading over these replies, I think it’s not that you are missing something, but that people have a limited knowledge of what is involved and how to do changes.
I didn’t see anyone mention that WP is unlikely to fix it so we better do something now that the 4.x support is questionable, (the editor being our biggest distinguishing feature from WP).
I wasn’t interested in whether the editor was upgraded or not. I got involved because it’s a puzzle (and I like puzzles), and it was bugging me to see so many clueless comments and speculations thrown around.
I don’t like the 5.x defaults or styles and I don’t think most of the standard Tiny plugins should be loaded, so for me it’s about making the new code run without being able to tell it’s changed. Seamlessly upgrade.
Yes, it’s kinda hard when the subject is a CMS, which only developers truly understand.