There will be a COS version of 6.0, expect that in a few months. The OPO may well get OOS 3.0 as well. But honestly, you don't want these updates quickly. If you want to see why go and download a 6.0 based custom ROM.
You can flash an unofficial cm13 build right now for your OnePlus One but there are some bugs with it. I'm sure soon enough the major bugs will be fixed though
Posted via the OnePlus One (Cyanogen OS 12.1 w/ Nova Prime)