15 years? I'd say no longer than 25 years -- if we're still carrying around computing devices by then (and it hasn't all just been subsumed into the cloud)
van der Waals' radius of silicon is 0.21 nm http://en.wikipedia.org/wiki/Silicon so current 19nm process nodes are already 45 atoms wide, there simply isn't much room for improvement left.
and it looks even deader for Flash than it does for CPU's, as ever finer processes are already producing ever slower and less reliable Flash cells. Those can be, and certainly are, mitigated by ever more extensive read/write parallelization and error correction in the controller, but only so much. "The drive is aimed at read-intensive applications" is a nice way to say that write performance sucks, relatively speaking.
So, if the semiconductor industry won't come up with something unheard of (which it just might, given the scale of the stakes involved) this might be one of the last radical upgrades available.
By 2030 seems like a fairly safe bet (barring major disaster before then).
[Edit: Yes, thanks, I meant TB, not GB. Fixed.]
Sounds reasonable, considering that we were at 1GB (HDD in laptops) 20 years ago.
Capacity will grow until it hits one of two types of limits: physics or the market. If physics doesn't allow for 1PB SSD in a notebook, you won't get it. If the market doesn't see the value in 1PB notebook disks (and I'd claim they won't see it, even after 15 years) you won't see notebooks with 1PB SSD.