Fedora 26 was just released last month, and it’s the most advanced version of the Red Hat sponsored operating system, supported with software and security updates for approximately 13 months, but Fedora 25 will still be supported for another four months or so, and upgrading to either release is OK. Of course, it is recommended that you upgrade directly to Fedora 26, but Fedora Project provides upgrade instruction for both Fedora 25 and Fedora 26, so if you’re still running Fedora 24 on your machines, please take your time and upgrade it so that you continue to receive the latest security patches and updated packages.