Since they are stacking ONO layers laterally in 3D NAND instead of vertically on floating gate, the lateral scaling of 3D NAND is probably already at/near its limit, but certainly the number of vertical layers is supposed to increase as much as possible. But eventually, the vertical channel gets too long.
It seems that NAND Flash have many more years of a roadmap. The 3D NAND started mass production with relativly old process node 40nm - 24 layers. It could scale up for over 128 layers and down to the 14/16 nm over time. These represent too many nodes, and accordingly years, to make any reasonable prediction at this time.
No doubt that a new technology would initially have its cost, but mature technologies have had years of cost-reduction methods applied and there is no reason not to include cost-reduction in new technology development as well.
Treating 3D NAND as a "new" technology, when can it get its cost appreciably down? Or will it be accepted anyway after 1Z, even if it is more expensive?
To me 10-12 years seems like a very short time to get a new technology in place when the profit margins on existing technologies will be under continued pressure. Where is the $ going to come from to fund significant new technology development, manufacturing plant and other infrastructure expenses... Wowzers!