Soon (April), it’s time to switch to ESM (without CJS backup) for all packages in the ecosystem.
That’s a lot of projects switching over, and a round of majors that bubbles from the bottom through to the top.

I’ve had some experience with that recently in a push in micromark (with CJS fallback, causing issues). My recent own projects dioscuri and xdm are fully ESM. It’s going to be a lot of fun for the ecosystem 😅

Otherwise, here are some changes slate for this next bubbling:

Big breaking changes:

• archive and deprecate remark plugins that (should) have rehype equivalents, and add some docs somewhere on whether folks should use remark or rehype plugins (currently quite confusing)
  • remarkjs/remark-external-links
  • remarkjs/remark-unwrap-images
  • remarkjs/remark-highlight.js
  • remarkjs/remark-react
  • remarkjs/remark-autolink-headings
  • remark-html-katex in remarkjs/remark-math
• archive and deprecate projects w/ very few downloads:
  • remarkjs/remark-midas
  • remarkjs/remark-defsplit
  • retextjs/retext-sentiment
  • vfile/vfile-reporter-folder-json
  • remarkjs/grunt-remark
  • syntax-tree/unist-builder-blueprint
  • syntax-tree/unist-builder-blueprint-cli
  • syntax-tree/hast-util-to-snabbdom
  • syntax-tree/mdast-util-from-quill-delta
• remark-yaml-config: update js-yaml
• vfile-matter: update js-yaml
• unified-engine: update js-yaml
• vfile-message: rename location -> position (Rename location field to position vfile/vfile-message#6)
• vfile: rename contents to value (Rename contents field to value vfile/vfile#49)
• mdast-util-to-string: do not use node.title (Remove node.title support syntax-tree/mdast-util-to-string#8)
• mdast: rename depth to rank (Rename depth to rank syntax-tree/mdast#31) (I feel the other issues there plus Rename node types syntax-tree/nlcst#6 are too much break for what they bring)
• hast: change doctypes (Simplify doctypes syntax-tree/hast#19)

Small breaking changes:

• hastscript’s h and s and a JSX pragma Add support for using h, s as a JSX pragmas syntax-tree/hastscript#15
• unist-util-find-all-before’s results should be reversed probably Results are reversed syntax-tree/unist-util-find-all-before#6

For ES++ features (unifiedjs/rfcs#4), I’d say we can do that after we switch to ESM, because ESM will already be a lot of work, and it gives us a baseline of what ES features / engines to support.