So is it safe to say by 2017 or 2018 we finally get price ratios cheaper than the HDDs we have today?
That is the million dollar question
I think that it will depend upon the maturation of new HDD recording techniques, which increase HDD capacity and reduce price-per-GB. Seagate has shown off HAMR HDDs, which uses targeted heating via lasers to increase density. HAMR will enable HDDs up to 20TB (and beyond), which may allow HDDs to stay cost-competitive for some time.
It is important to remember that there is not enough flash-fabbing capacity now, or in the projected future, to even scratch at the amount of data that needs stored.