On June 25 Cyanogen announced they are finalizing the branches of CM11 and CM12 as they shift their efforts to working on CM12.1 (based on Android 5.1.1) and Android M releases. According to the CyanogenMOD team CM11, based on Android 4.4.4 Kit Kat, and CM12, based on 5.0.2 Lollipop, have not seen any major development in the past few months, thus the final snapshot releases (not nightlies) are going live on the 25th. Nightlies and weeklies for the two branches will be slowly phased out and likely shut down when Android M enters the nightly release phase.
CyanogenMOD states that users should not have any issues upgrading to the final releases of CM11 and CM12, though users upgrading from 11.0 to 12.0 should upgrade their recoveries to prevent any issues caused by the SELinux kernel module (Security-Enhanced Linux). The team also notes that bugs can still be submitted but CM11 issues, unless they prove to be very critical, are not likely to receive a lot of attention. CM12 bugs will be addressed, as the code base between CM12 and CM12.1 are so similar that a bug on one is also likely present on the other.
Oddly enough CM12 has gone straight from nightlies/weeklies right to a stable final version, bypassing the so called "snapshot", or M, release phase that occurs every month or so, though considering how quickly Android 5.1 was released after 5.0 this is not surprising. CyanogenMOD also addresses why they bothered with another CM11 release at all, considering it is based on Kit Kat. According to CyanogenMOD many users have been slow to upgrade to Lollipop (CM12), which they attribute to either a lack of a snapshot release or adverse reaction to Material design. Considering the large group of CM11 loyalists CyanogenMOD felt compelled to do a final release showcasing the best that CM11 has to offer. Perusing the comments on CyanogenMOD's blog post revealed that a relatively small number of users are dissatisfied with material design, most reported they had not upgraded due to the lack of a CM12 build being ready for their device of choice. Regardless which release you are loyal to both are going live at the same time, so get your devices ready, backed up, recoveries updated, and as always, happy flashing.