Mel Choyce recently published a working docoment for tickets and improvements under consideration for WordPress 4.9. Among them are improvements to the code editor, customization efforts, better theme switchingm, improved processes for uploading updated theme and plugin zip files, iteration on media management, and adding customizer endpoints for Gutenberg to leverage.
I never recommend the current WordPress code editor. I've long been on team “remove”. Mel makes a good argument for making these improvements. I'm hesitant to say it's a good idea, but I've long been an advocate for supporting improvements people want to work on, and if this is a priority for enough contributors, that's good enough for me.
4.9 will not be a bombshell release, and again, that's fine. A couple of these features a really long overdue (like uploading plugin updates by zip, or fixing the “front page” mess). And the largest efforts are being put toward Gutenberg, which has undergone massive iteration.