Better late than never. OnePlus X customers will be happy to hear that OnePlus released Oxygen OS 3.1.2 today, which will update the OnePlus X to Android 6.0.1 more than one year after its initial release.
http://www.notebookcheck.net/The-OnePlus-X-is-getting-Android-6-0-1-more-than-one-year-after-its-release.178711.0.html