The OnePlus 3 and 3T are two of the most highly-regarded phones that OnePlus has released to date, and leading up to the announcement of the OnePlus 5, there was some concern surrounding whether or not OnePlus would actually continue to update its older hardware. Android O is still scheduled to be released for the handsets, but according to a Q&A that OnePlus shared on its forums, you shouldn’t expect any major software updates following it.
OnePlus will not be pushing out any major software updates for the OnePlus 3 or 3T following Android O. The company will also be stopping the Open Beta Program for the handsets after Android O and use it exclusively for the OnePlus 5.
OnePlus has been pushing updates to users on the Open Beta Program around every 1-2 months since its release, and seeing as how the beta has been used to test new features before releasing them to public builds, it only makes sense that these will be ended as well.