Apple offers no end-of-life roadmaps for its operating systems, and it doesn’t officially comment on whether support has dried up for this or that version of OS X. The best you can do is look at historical data. Since switching to a yearly release cadence with Lion back in 2011, Apple seems to be willing to support whatever the latest version is plus the two preceding versions. When OS X 10.9.2 was released earlier this week, it was accompanied by security updates for OS X 10.8 and 10.7 but not for 2009’s OS X 10.6.
It’s the first major security update that Snow Leopard has missed—the OS is still getting iTunes updates, but its last major security patch happened back in September. This has prompted a flurry of posts from various outlets. All point out the same Net Applications data that says 10.6 still powers around 19 percent of Macs. Most compare the OS X support cycle to the much-longer Windows cycle. Some make a bigger deal about it than others. None really tell anyone in that 19 percent what to do next.
You’ll need to know the exact kind of Mac you’re using before proceeding—typing your serial number into this Service and Support page should give you the information you need if you’re not sure. Launching the System Profiler application from the Utilities folder will show you your serial number and your Mac’s specific model identifier (something like MacBook4,1 or iMac11,2), the latter of which can be used with this EveryMac lookup page to find what you’re looking for.
Newer Macs: Upgrade to Mavericks (or at least Mountain Lion)
Macs this applies to: Anything that can run Mavericks. See this post for more details.
If you’re still running Snow Leopard because it came with your Mac and you just never got around to upgrading, the good news is that basically any Mac that came with Snow Leopard can update to the latest version at absolutely no cost. Just grab it from the Mac App Store and do an in-place upgrade—you shouldn’t run into problems, though it is probably a good idea to run a Time Machine backup (or something similar) before doing it.
New OS X versions usually have teething issues when they first come out, but the 10.9.2 update is a big one that fixes much more than the “goto fail” SSL bug. If you were holding out because you didn’t want to deal with those early-upgrader blues, most of 10.9’s largest bugs should be squashed at this point.
Supposing your hardware can handle the upgrade but you don’t care to move to Mavericks, you can still purchase copies of Mountain Lion for $20 through Apple’s online store. The company will send you a code that you can redeem in the Mac App Store, and you can use that version of the software until you’re comfortable moving to Mavericks or until software support for OS X 10.8 dries up.
Full Story: Snow Leopard updates are probably done—here are your OS X upgrade options | Ars Technica.