If each layer was 50 nm high, and you built the chip up to an unrealistic 1 centimeter high (eg, a 1 cm^3 chip instead of 1 cm^2), chosen because that would pretty easily fill a 2.5" drive, that would give you:
(1 centimeter) / (50 nanometers) = 200,000 times today's capacity.
Which is only only 18 doublings, or 36 years more of Moore's Law (assuming the pessimistic 24 month end), or roughly the gap between a Commodore 64 and a decent laptop today. Some people still working in the industry have gone through a larger increase. I've gone through a 1000 fold myself, and I'm only 25.
There are sure to be a whole bunch more we can do to get more capacity, but it's pretty mind blowing to think that the theoretical limits to storage are within our lifetimes on an exponential scale. So as much as Moore's law hasn't failed us yet, it certainly will at some point (probably in the form of the doublings themselves exponentially taking longer and longer).