A few months back OnePlus announced that it planned to launch updates based on Android 6 for the OP2 and OPX and today the company is reaching out to the community for beta testers.
The notice was posted on Weibo, so at this stage in development it looks like OnePlus are only interested in Chinese Oneplus users.
Gizchina News of the week
OnePlus 2 users wanting to be part of the beta program need to be comfortable flashing ROMs manually and be willing to report bugs etc to OnePlus.
No doubt the Android 6 update will be leaked at some point during the beta but keep in mind that that Chinese version of the OnePlus OS and the international one are very different beasts (the Chinese version only having English and Chinese language, limited features and no Google support from what we remember) so think twice before jumping the update queue.
Sorry OnePlus, you need to get an invite first
Sorry owners of OnePlus One, your phone is too old
And Jiayu S3 still in 4.4 and 5.1.1 RC2… sniff