I'd love to see any analysis that shows $/GB for SSDs matching that of hard drives in two years time.
Maybe it does if you extrapolate from the past five years, but if so it totally ignores economics (you know, supply and demand) because Chris is right, the capacity exists to make only a few percent of the total TBs of hard drive output in the form of flash. Even if you assume a very optimistic 10x growth in flash bits and demand growing at 0% over the next two years, there isn't nearly enough flash to go around! The result, the steep drop in $/GB flash prices is going to hit a floor far enough above $/GB hard drive prices to compensate for the performance difference, as economics says it should.
Such a floor would add some certainty for the investment required to build additional flash fabs, but we're still talking a minimum of a decade before enough capacity could come online to replace hard drives. Probably longer given how insatiable the world's storage appetite is. Luckily, there is little reason to replace hard drives in a lot of roles that consume a lot of hard drives. For archival backup where tape is too slow, or disk to tape backups, flash gains you nothing. Ditto for applications that require a lot of capacity and sequential I/O - flash gains you nothing over striping a bunch of hard drives together.
Much storage isn't performance sensitive to the point that all flash offers any advantage over a two tiered approach with 5-10% flash for the hot spots and 90-95% hard drives for the rest. I will agree that all laptops/desktops shipping in 2-3 years will be all flash, simply because the per bare drive minimum price is lower for flash than hard drives, so once the amount of flash included in those minimal drives is sufficient for a $250 PC (let's say 250 GB) that's what it will include.
It remains to be seen how long the strings of 3D NAND can be made, but the most optimistic projections I'm aware of show it petering out somewhere between 128 and 256 cells. We're already at 32, so there's not much more to look forward to there unless they figure out a way to extend that. If they don't, NAND $/GB hits a wall, and we better hope for a competing technology like memristors to pan out!