Why would price per TB be the same? The whole point of cramming more levels into the same cells is that you can store more data in the same number of flash cells.
Because you get Cost efficiency from newer tech, ( cost reduction with adding layers are not linear ) but current SSD price are at zero or negative margin. ( There is an oversupply or under demand of NAND ) Which means should this tech arrive they are only going to gain back their reasonable margin. Hence the 4TB might be priced the same.