The OnePlus 5 and 5T are still under two years old, as the 5 was released in June 2017, and the 5T came out in November of the same year. If you were still a bit concerned that either phone would miss out on Android Q, you can rest easy — OnePlus has confirmed that both devices will (eventually) get the update.
In a forum post, OnePlus said, "We have already released Android Q Developer Preview on the forum for the OnePlus 7 Pro and OnePlus 6/6T, available. For those wondering, rest assured: Android Q will also make its way to the OnePlus 5 and 5T. Just remember, there are no ETAs."
This news comes shortly after Android 9 Pie began rolling out to the OP3 and 3T, two phones released in 2016. This announcement makes no mention of those devices, so it seems Pie is the end of the road for them — custom ROMs aside.