OnePlus is finally rolling out an update to its alternate ROM. The new update comes not in the form Oxygen but Hydrogen OS version 3.0. The new update brings with it Android Nougat and a whole lot of other changes.
However, the ROM is for the Chinese version of OnePlus 3 and 3T. But if you want to check out the update and experience something different then you can flash your device firmware and easily install the update yourself from recovery. It will work on the regular or international variant of the OnePlus 3 and the OnePlus 3T.
The ROM is available in Chinese and English languages and you might find few Chinese apps with the update which you can easily delete. Also, as the Hydrogen OS is a firmware for the Chinese variant, it doesn't come with the Google Apps pre-installed. You will need to install it separately.
Other than that not much details have been presented about the new Hydrogen OS 3.0, but we should get the changelog soon and it will all be clear.