I see still a long time till the demise of the HDD, so I'm not worried about HDD companies going out of market anytime soon. Most people that say SSD is the future and capacity is enough for them still use the cheap HDDs for backups and to store big data (pictures, movies, ...). And don't forget that not all computers out there are laptops or desktops there are huge computer systems with thousands of HDD, replacing all that storage by SSDs is prohibitive, having hybrid disks might be a good way to have a performance/capacity/cost trade-of.
Eventually HDDs will be replaced by some future tech (and that tech may not even be SSDs), but it's amazing that HDDs have been able to keep with technology and have been with us for almost 60 years.