In a post earlier this evening Cyanogen Mod announced that they will not be working on a build based on the new Android L Developer Preview. This is to be expected. While it is nice to have early access to the next great thing it turns out that this build is unfinished. There will be changes before the final build of Android L is released. This means that Cyanogen Mod could potentially waste weeks of time integrating CM features on a build that could one day have big changes that break these features.
While they will not be jumping on CM12 today they will still be checking out the Android L Preview code becoming familiar with it. The process will ultimately allow CM to get a more stable build out once Android L is made official and final. CM11 M8 4.4.4 is slated to be released on Friday July 4th. They will continue the M release cycle until there is some sign of a final release of Android L. You can head to CM's blog post by following the link below for the full details.
Via CyanogenMod