As far as I can tell, it's been like this SL - Intel processor, 1GB RAM Lion, ML and Mavericks - Core 2 Duo, 2GB RAM Even some iMacs from as far back as 2007 can run Mavericks, all unibody Macbook pros can and even the Macbook aluminum from 2008. and it looks like anything from 2010 or newer can run it for sure. Is it possible that they increase the requirement to Core i3 and 4GB of RAM for the next one, or do you think there's enough performance overhead in a C2D w/ 2GB for the next version? How about Core i3 and 2GB RAM, which would allow machines from 2011 and newer? If 10.10 comes out in 2015 that's still 4-year-old machines being able to run the latest version. I just find it hard to imagine that in 2015 they'll still be supporting devices from 2007-2008, but it would be a good thing the leaner and lighter it can run, obviously. I know nobody here has insider info...just speculation.