The flattening of the CPU speed curve wasn’t matched by the GPU performance curve. The difference between linear computation and graphics cards is the latter is parallelizable, and the former is not. Flash is also trivially parallel.

Even with perfect materials, a 10 millimetre CPU couldn’t be faster than about 30 GHz because of the speed of light, but even current microSD cards have enough bits-per-unit-volume to put 1.2 petabytes in the largest current standard form factor of hard drive (at a cost of £704k/$982k/€798k). I don’t know how much of that volume is wasted on plastic casing or circits that would be redundant if you really wanted the highest possible density, but then again I also don’t know how much waste heat they produce either.

My claim is primarily that costs can and will fall, as to presume capacity will rise requires something that uses a lot more data than even high quality video currently uses. (Full mind backups would be one of those things, but IDK when to expect that).