OnePlus have finally announced a date release for their Android Lollipop 5.0 on their forum today. The Chinese manufacturer who used to work closely with Cyanogen parts ways due certain disagreement. OnePlus decided to build its own Android-based ROM called Oxygen OS.

The reason for delaying the timeline to release their Oxygen OS after separation, OS requires to be signed by Google in order to shipped with playstore officially, the firmware would require time to adjust and remake, drivers such as camera, Wi-Fi, modem baseband and etc. OnePlus have provide official dates as such:
Cyanogen have provided the last version Lollipop build to hand off everything to OnePlus hence stating CM 12S, will be released before March 30, 2015. Oxygen OS, OnePlus own Lollipop-based Rom will be available either on March 27, 2014 or earlier.

OnePlus have also warrant that if they missed any of the above deadline, five 64 GB OnePlus One smartphones will be given away. To join the giveaway, one must register on the OnePlus forum and reply to the announcement thread.

Source: OnePlus forum