Oneplus one cm 12 update is out.
People are getting the OTA update randomly (Source – oneplus forums )
But if you dont want to wait then here are the details to do it manually,
Step 1. Download the CM12S Android Lollipop Zip file for Oneplus one here and Don’t extract the folder.
Step 2. Move the downloaded ZIP file on the phone. You need to flash this file manually form the recovery mode.
Step 3. Turn of your Oneplus one and boot into recovery mode. To do this Press Volume Down + Power button.
Step 4. Now you are in the recovery mode. Wipe the following > (If you are on CM11S Wipe > Dalvik cache, Cache)
(if you are on Oxygen OS and CM12 nightlies = Wipe > Dalvik cache , Cache , system, data )
Step 5. After that Go back and start the flash process.
Step 6. Tap on install. And Locate the CM12S zip that you moved on you phone one Step 2 and Flash it.
Step 7. One the flashing process is done. Reboot to system.
Step 8. The first boot will take 5-6 minutes.
Enjoy! Now your phone is running on CM12S Android Lollipop.