OnePlus, back in January said that the OnePlus 2 will receive Android Nougat, but there's no update till date and users of these phones are going crazy regarding the update.
In OnePlus forums, users have created various thread raising their voice towards the update. The OnePlus 2 surely has the hardware inside it to run the latest OS. However, the OnePlus X's hardware is outdated, and the company earlier said that the OnePlus X can not handle graphics of Android Nougat.
If you notice, the official Lineage OS builds for both the OnePlus 2 and OnePlus X are available. So, OnePlus should consider this and release the update at the earliest for both the phones.