At the time of debut, OnePlus 2 was considered as a phone that will be one of the most powerful devices available in the market for a long time. However, this prediction turned out to be wrong, as can be seen after OnePlus plans for future of this phone.
OnePlus 2 was supposed to receive Android update to 7.0 version some time ago, at least according to declarations of OnePlus company, but it hasn't appeared until today. As it turns out, this will never happen. One of moderators on official forum of company posted this message: "When we built the OnePlus 2 we didn't have the software infrastructure team in place we do now". We can easily deduce that OxygenOS won't be released in version with Android 7.0 and if users want to have Nougat in their phones, they must use unofficial versions of system.