Microsoft have released the Developer Preview for the latest version of SharePoint: SharePoint 2016! Being a developer preview, the interface (and potentially UI functionality) is not final, but the API is close to it (and it’s due out first quarter next year, so it’ll have some bugs in it too) – Full article is here: https://blogs.office.com/2015/08/24/announcing-availability-of-sharepoint-server-2016-it-preview-and-cloud-hybrid-search/
SharePoint Server 2016 further empowers your workforce by delivering a consistent experience across screens, whether using a browser on the desktop, a mobile device, tablet or slate. Through this rich experience, users can easily transition from one client to another without having to sacrifice feature fidelity.
Responsive by any other name smells just as sweet.
Q. Can I upgrade SharePoint Server 2016 IT Preview to RTM when released?
A. No, SharePoint Server 2016 IT Preview cannot be upgraded to RTM.
Fill yer boots!