The release candidate for WordPress 4.7 is available since November 24. The final version is expected to be released around December 6th, 2016. It will be the last major release of this year. As is the tradition, it will come with a new default theme for the next year (see A preview of the upcoming Twenty Seventeen Theme).
Also WordPress 4.7 will allow users to switch the admin language from their user profile. This means each user can choose the language he prefers independently! The thumbnail preview for PDF uploads is another great improvement coming along.
An outstanding new feature is the custom CSS editor that enables users to make CSS changes to a Theme without the need to create a Child Theme. Creating a Child Theme allows you to add custom code to a Theme protected from being overwritten the next time the Theme is updated. Not using a Child Theme but modifying Theme files directly causes the loss of all changes the next time you update the Theme.
So usage of a Child Theme was a must yet for anyone to make changes to a Theme. WordPress 4.7 will give you the option to add custom CSS to your website using the brand new Customizer’s custom CSS editor.
With this live CSS editor it will be easier than ever to add custom CSS. Users who used Child Themes so far solely to add some CSS rules will be able to drop that. For advanced Theme customization usage of a Child Theme will be indispensable in the future.