The new toolbar from Google Docs is just a part of a bigger redesign. Apparently, Google Docs will replace the tabs with a traditional menu and will switch to a "print layout", the default view in Microsoft Word. It's not clear whether Google Docs will also add pagination, but I don't see the point of adding a print layout without actually showing pages.
The slightly-edited screenshot is from a presentation that shows some of the tools used by Google employees, who have access to not-yet-released versions of Google's products. Philipp Lenssen describes some of Google's internal tools, while Brian Ussery has more details about the presentation.