Mavericks will run on 2008 Macs. 2008. By the time it comes out, that’ll be machines which are nearly 6 years old. Say what you like about Apple, but you can hardly say they restrict their laptop/desktop users from upgrading to the latest version. On top of that, one of the guys from 9to5Mac says the Mavericks beta is giving him roughly a 100% increase I’m battery life on his 2009 MBP. Whether that’s borne out by other reviewers is yet to be seen, but again, Apple bringing new life to old hardware.