This is the second year running that a new OS X version has supported the same Macs as its predecessor, following three releases that all dumped a handful of Macs. MacBook (13-inch Aluminum, Late 2008), (13-inch, Early 2009 or later).Any Mac that can run OS X 10.8 or 10.9 can also run 10.10, a list that includes Macs from as far back as 2007. Luckily, most iOS and OS X users are getting off easy with iOS 8 and OS X Yosemite.
With rare exceptions, new versions of iOS and OS X usually don't make it to a handful of older iDevices and Macs, leaving owners of those gadgets stuck with old software or pushed into upgrading. The downside of new Apple software is that it usually displaces old Apple hardware.