There's a recurring theme in technology; older technologies have longer lifetimes than you might think. We're a long way from ssd being cheaper per bit than rotating hard disk. Sure, Moore's law says ssd gets ever cheaper, but so does rhd. Ssd has a number of advantages that offset the higher cost, but they aren't always compelling in every application. Ssd densities have already pushed the physics to the point where exotic data allocation strategies are needed to compensate for "wear-out" effects (yes, in solid state) so the slopes going forward won't be as different as you might think.
It's not the same technology, but the same concept: I'm reminded of the advice "Never underestimate the bandwidth of a station wagon full of magnetic tapes driving up the interstate". Fiber optics isn't necessarily faster for data transfer. Depends on how much data, and what your latency requirements are.
Do I want a rhd in my iPod? No, in fact I held off buying an iPod until flash versions became price competitive about 6 years ago. But as backup storage in a server room, even if it becomes another layer in the storage hierarchy with ssd "caches" in front of it, rhds will hang around longer than you think. The rhd manufacturers aren't ignorant of ssds, and when the business stops making sense, they'll stop making them. Most of them are, or can be, in the ssd business, they'll sell what they can make money selling, and the cost of entry to flash technology isn't that high for an existing rhd company. In a lot of ways, it's the same business.
But if they still think they can make a competitive product with acceptable sales volumes by pushing the areal density of rhds another 25% every couple of years, by doing things like using helium to reduce head gap height, then they'll keep pushing the technology.