Shiny Updates: WordPress 4.6 will introduce “shiny” updates. Users will now be able to update and install plugins and themes without being redirected to the progress screen.
Goodbye Google Fonts: Native System Fonts in WordPress Admin Area
WYSIWYG improvements:
Users can restore WordPress posts from browser backups and autosave even when they have revisions disabled.
Adding a broken URL will be highlighted.
New functions and classes:
register_meta() - function for the registration of meta keys
WP_Post_Type class which changes $wp_post_types to an array of WP_Post_Type objects.
WP_User_Query, WP_Comment_Query, and WP_Term_Queryclasses in WordPress 4.6 will provide a better structure for generating, similar to WP_Query