This should come as no surprise, but CyanogenMod has put out a blog post last night that they aren't putting a priority on the Android L release just yet. And the biggest reason is that it's only a developer preview right now and not final. So why waste their time with CyanogenMod 12 when it might completely change when Android L is released in the fall. Right now CyanogenMod is still focused on Android 4.4.4 and perfecting KitKat or CyanogenMod 11. Lately, CyanogenMod hasn't been about being the on the bleeding edge, but more about stability, which is a great thing. Some like to flash ROMs for the bleeding edge stuff, while others like to do it for stability, and because their carriers aren't supporting their device anymore.
As far as the OnePlus One goes, that's running on CM 11S, or Android 4.4.2, we should see an update to Android 4.4.4 soon, but Android L isn't coming any time soon. While that also shouldn't be a surprise to anyone, here's an excerpt from their blog post about their roadmap:
CM11 M8 (Android 4.4.4) release is already tagged and branched and in preparation for release just after the July 4th weekend. Until we get a signal or indication of when "L" will be final, we will continue to treat it as a secondary to closing out bugs and improving features/support for CM 11 and continuing the 'M-release' cycle."
So there's that. This isn't really anything surprising. Because the developer preview could get a huge overhaul between now and the fall when it ships, it makes sense that ROM developers like CyanogenMod won't be getting in on cooking up their Android L ROMs anytime soon. As they could be wasting all that time. As much as we want Android L, we'll have to stick to the Android L themes for CyanogenMod for now at least.