Just wanted to give folks my perception and feelings on of how we’re doing thus far with the core foci: Writing: I’m really happy with the progress. It has had some slower weeks here and there the past few months, but by and large the technical prototypes we implemented have been successful and we’re ready to move into the next phase. We have a Chrome fix we have to get in the next minor release, and the link boundary improvements will be going into TinyMCE core and could be great for an interim +0.1 release.
Customization: Doing well. Remember: The plan is for the larger block-driven customization work to kick off in June. Prior to that, we’re focusing on widgets and other low-hanging fruit. Lack of developers slowed us down last few months, now doing better but could still use more help there. Media widgets + WYSIWYG on text widget seem simple but will have a big user impact.
REST API: There has been little to no perceivable progress on having any parts of wp-admin powered by the REST API.
Considering 4.8: The TinyMCE inline element / link boundaries, new media widgets, WYSIWYG in text widget, and perhaps something else small like the WordCamp / meetup dashboard