updates team is working on bringing a smoother experience for managing plugins and themes to WordPress [through] improving perceived performance and limiting confusing notifications.” make.wordpress.org/core
install, and delete your plugins and themes. These actions are now accomplished within their respective pages using AJAX for a better user experience. This has been available for updating Plugins since 4.5 but now applies to themes, translations and more of the WordPress environment.
and Page editor for a while, it now leverages your browser, saving the post title, content and excerpt every 15 seconds. As you type, WordPress saves your content to the browser.
to have a full website backup (database and files). • Check the themes and plugins in use on your site for compatibility with WordPress 4.6 (or any other major WP core update). • Where possible, apply updates to a test/staging environment so you can test the changes before applying them to your live site.