So it seems that OnePlus is maintaining its strange twice-yearly release cycle with the to-be-fully-confirmed announcement of the OnePlus 5T. There were rumours a few days ago from some blogging site, namely GizmoChina, that initially started this. But now it seems that even oppomart.com (an official store front for Oppo and associated companies, including OnePlus) has made mention of the 5T... I purchased the OnePlus 5 and I don't regret it (so far).
Only difference thus far that I can find are:
1. Screen - 5.9 inch, full HD (1920x1080 pixels), Optic AMOLED, 2.5D Corning Gorilla Glass 5.
2. Fingerprint scanner - On the rear.