Flash only got competitive after both HDDs and DRAM scaling slowed, allowing it to catch up, and end up in an interesting position between them.

There are about a dozen upcoming memory technologies with better theoretical headroom waiting in the wings for DRAM and Flash scaling to slow down. In the early 10's it really looked like Flash was about to be replaced, but then Samsung managed to move Flash to the third dimension. Very soon, either DRAM does the same, or it gets replaced by something.