"This image covers the basic features of 3D Xpoint. The new memory is designed to be non-volatile, stackable (to improve density), and can perform read/write operations without requiring a transistor (DRAM requires one transistor per cell, which is one reason why it draws much more power per GB than a NAND flash drive)." ----
Maybe transistors can't get smaller, but you don't have to use transistors. 3DXPoint is not as fast as DRAM but it is still so fast that it can replace DRAM in many applications. So the total amount of DRAM (and thus the number of transistors) required is greatly diminished.