Cyanogen announced the final "snapshot" releases for CyanogenMod 11.0 (Android 4.4) and 12.0 (Android 5.0), as the company and the open source community supporting the CyanogenMod project start working on Android M (presumably CyanogenMod version 13). Snapshots are versions of CyanogenMod that are more stable than "nightlies" but less stable than "release candidates."
CyanogenMod is an open source project that officially supports hundreds of devices, and it should not to be confused with Cyanogen OS, a proprietary version made for commercial smartphones such as the OnePlus One.
To the surprise of many, the company released another snapshot version for the KitKat-based Cyanogen 11.0. The reason given was that many CyanogenMod users are stuck on CyanogenMod 11.0 despite Cyanogen 12.0 being available for their phones.
Apparently, many users either considered KitKat to have been a higher-performance version of Android than Lollipop, or they simply didn't like all the animations and white space introduced in Android 5.0. This compelled Cyanogen to offer another stable (and final) version of CyanogenMod 11.0 with all the latest bug fixes and security patches.
Users who are finally ready to move to Lollipop and the final snapshot version of CyanogenMod 12.0 are advised to also update their "recoveries" to ensure SELinux support doesn't give them any trouble with the new version. According to the company, the users of CyanogenMod 12.1 shouldn't have any reason to downgrade to any of the lower two versions.
Nightlies and weeklies for CyanogenMod 11.0 and 12.0 will be slowly phased out and then entirely shut off, as Android M nightlies begin to appear online. The CyanogenMod 12.1 nightlies will continue as normal.
Cyanogen doesn't expect further work on CyanogenMod 11.0 to happen in the future, unless there are some new 'ultra-critical' bugs that show up. CyanogenMod 12.0 bugs should continue to be fixed, as the codebases between CyanogenMod 12.0 and 12.1 are very similar, and the bugs would likely affect them both.