Believe it when I see it.
The proper technical term is ...
Inevitable
They are already more cost-competitve than hard drives of several years ago. All we need is for hard drives to hit a capacity wall and SSDs will catch up. My SWAG is that hard drives have already milked 80% of the perpendicular recording tech that hit a few years ago and let us go to terabyte-plus.
You will. Mechanical drives are on their way out. It does not mean that mechanicals are not still viable; I just picked up a WD USB "Book" for $120 (1TB) that should last a while. But when SSD comes down, I will be replacing my aging internal mechanicals with them. Energy saving, speed, quietness are all appealing benefits.
So, count on it.