• Quip/Ulysses-like links — https://cloudup.com/cgXAgatVlps — a UI affordance showing the boundaries of the element, allowing you to know when the caret is inside the element vs. outside.
• Same as the above but for code blocks (through button or backticks).
• Spurious markup on blockquote when replacing content. (Ticket.)
• Option to strip all attributes on paste, except when pasting internally. (Added by @iseulde.)
• Fix some contenteditable=false bugs: contenteditable=false enter/delete issues tinymce/tinymce#3325. (Added by @iseulde.)
• Make sure we have good test coverage for pasting from Google Docs. https://github.com/tinymce/tinymce/blob/4.5.3/tests/plugins/paste.js#L217 (Added by @iseulde.)

https://core.trac.wordpress.org/component/TinyMCE
https://core.trac.wordpress.org/query?status=!closed&keywords=~upstream&component=TinyMCE