We seriously know nothing about RNDA 2.0, AMD has not said anything about it other than it will have hardware RT. They are basing this all off of RDNA 1.0's efficiency gains, which was has a 1.25 percent increase in IPC. We won't get a closer idea of how powerful it is until AMD releases those details, also need to know memory bandwidth numbers, CU count, and several other factors. All I know is that MS is undoubtedly sold themselves short by saying "2 times as powerful as One X" but it is obviously more powerful than just 2 times, just how much more powerful we don't know.
Anyone saying 3-5 times more powerful is just making s*** up, including the looney bins here and the tech youtubers.