Shortly after apple release 10.12 they will probably release a security update for yosemite and not for mavericks, i.e. drop support for mavericks (at least as secrurity updates are concerned). So will you upgrade to 10.10 (or 10.11 or 10.12) then? Or before then? Or will you still keep using mavericks after that? Many people have stayed with mavericks till now despite 10.10 and 10.11 being released already. That has been OK so far because apple are still supporting it with security updates at the moment. Up till now whenever a security update for yosemite as been released there has also been one for mavericks. But if they drop support for mavericks in the same manner in which they have dropped support for previous systems then it is unlikely they will keep supporting mavericks after 10.12 is released.