[citation][nom]alidan[/nom]funny you mention that, i just did math a bit ago on the intel 14nm process. lets assume that chip size means nothing, because i cant find chip size of ssd boards so just pcb thickness of 1.5mmplaying cards have an area of about 5645mmand are about 15.87mm thickin order to even cram 1/4 a pb into that area, you need to be at about a 9nm process. for a full tb, you need to be at a 4.5nm process. now i don't know about storage, but at least with the cpu, i remember it being said that 6nm would be the limit. well, 6 or 7 but 6 stands out more.[/citation]
Petabyte SSDs are probably never happening with current technology, for exactly the reasons you state. We'd need to increase the storage amount per cell pretty dramatically, and there are already problems with MLC drives compared to SLC.
Magnetic disks, however, may well reach that capacity. There are some interesting technologies on the horizon, which I can't remember exactly what are called, but promise to greatly increase storage density on magnetic disks. Using lasers to heat up the platter before reading and writing to be able to manipulate smaller portions of the platter, for example.
Assuming Moore's Law holds for magnetic disk storage density (and I have no idea if it's even holding now), we'd need to go from 3TB to 1000TB, ignoring the fact that current drives aren't really 3TB and 1000TB isn't really a PB. That's about eight and a half cycles, for lack of a better word, of Moore's Law. With each one being 18 months long, and rounding up to 9 cycles, we'd be looking at 1PB HDDs in 2Q 2025.
There are a LOT of ifs involved, though. Honestly, I'd be surprised if magnetic disks were still in use in mainstream applications in 2025. We'll probably be eyeing the successor to SSDs by then.