As per a  post on the Adobe blog yesterday, Lightroom 6 when announced will only work on 64 bit platforms.  This means Mac users must be on OSX 10.8 or above and Windows users must be on Windows 7, 8 or 8.1 64 bit.More info at http://blogs.adobe.com/lightroomjournal/2015/01/update-on-os-support-for-next-version-of-lightroom.html