Valve announced the first preview of upcoming SteamOS with code name "brewmaster". Upcoming SteamOS is based on Debian 8.1 stable release. In disclaimer, valve says that, current release is only a early preview and will be having limited hardware compatibility only. And this release is intended to get feedback from community.
From official release announcement:
Valve is pleased to announce the preview of the next SteamOS release, codenamed "brewmaster" and based on the latest Debian 8.1 stable release. Please note that this is a very early preview release and we have done only limited hardware compatibility and functional testing. We are releasing this early to get feedback from the community. You should not install brewmaster on any machine containing data you are not prepared to lose completely.
Although there are a lot of changes under the covers, the overall functionality and experience of brewmaster is the same as alchemist and most of the SteamOS FAQ applies to both releases. Continue Reading