Harari says they have three or four generations, five at most to go. Beyond that, NAND flash memory won't cut it anymore:
>i>The problem is that the different subcomponents inside these chips can't be shrunk much further. One layer, called a tunnel oxide, can probably be shrunk to about 80 angstroms. In other types of chips, this layer can be shrunk to 12 angstroms.SanDisk is experimenting with a couple of new technologies to overcome these problems like stacking transistors in 3D arrays and putting more bits in each cell.
Data corruption is another problem. Flash memory records data by storing electrons in cells. "At 32 nanometers, you can't afford to lose more than 30 electrons" before data corruption becomes an elevated risk, he said. "Thirty electrons sounds like a lot, but it is very small." The debut of 32-nanometer chips will be sometime toward the turn of the decade.
The turning point may come with the 20-nanometer generation of chips, which will start coming out a few years later. At that point, NAND chips will be capable of holding 256 gigabits of data, and the cost per bit will be about a tenth what it is today, but it will be extremely difficult with current manufacturing technologies and materials to go further.