Terabyte is already common in desktop hard drives. At recent storage-capacity increase rates, though, 150 TB is more like 2025 than 2020. Average increase rate is a doubling every 18 months to two years. Generally 18 months for SSDs.
Spinning-platter drives currently top out at 4 TB, SSDs at just shy of 1 TB. (Not counting truly insanely expensive completely custom models.)
2020 is 8 years away, or four platter doublings, five SSD doublings. So we're looking at 64 TB for spinning-platter, and 32 TB for SSDs. And there have been stalls in capacity increases before. We seem to be just ending one now. (We were stuck at 3 TB for over two years, and only squeaked out a 4 TB.)
Seagate just announced a "breakthrough" a couple months ago that they say will allow for 60 TB desktop hard drives... Just over a decade from now. The first drives with these capacities aren't out yet - the first doubling of 3 TB in three years.
Plus, the highest-capacity models always significantly more per storage unit (GB, TB...) than the next-largest model, so the highest-capacity models are never the most cost effective.
Sorry, but I think we're looking at 150 TB being "at your local Fry's" more like 2030-2035.
And at this point, we're reaching a point where movies are the only thing that take up tons of space. Like music before, the vast majority of computer users can do without massive amounts of storage. Yes, there will be a market for large drives, always, but very few users nowadays have any true "need" for a 4 TB drive now, a good majority don't even need the more reasonably-priced 2 TB. With 4K+ video being the only major driver I can see for dozen+ TB storage, I just don't see a "home market" for a 150 TB drive even by 2040. (Especially with the move to "cloud storage" of things like music and movies. Thanks to iTunes in the Cloud, my laptop just got to drop 40 GB of locally-stored files. And once I can do the same with all of my movies (not just iTunes-purchased ones,) I will be able to drop another 200 GB.)
The only reason I have 4 TB of total drive space (across three hard drives) on my desktop is because I am a prolific HD home movie filmer - and am terrible at editing them down and deleting the (large) raw footage in a reasonable period of time. If I were simply faster at editing the footage, I could easily work with just 1 TB of storage.