I’ve read through the changelog on master, but just wanted to know if there was a top-line summary of what things were being planned for 4.x? I’m in the middle of building out a few sites, and I’ll be mindful of what breaking changes may occur between 3.x to 4.x…just wanting to know what kind of features the dev team is most excited about so I can dream ahead 
Remove the partials_dir setting. Partials should live next to content, or be addressed with absolute paths.
Booooo… I love partials_dir, since partials usually are not part of content, but part of “mechanics” of the site. Menu, sidebars. My 3cents…
I just noticed that. I’ve found a project structure that works well for me. Even if I have to address partials with absolute paths, I’ll keep having a folder acting as a fake partials_dir.
I do the same as you, I use partials for menus, headers, footers, etc. not for actual content.
What is the motivation for this change?