They're looking solely at STRs, which is the one metric which largely doesn't matter for most users. The key metrics are total cost, cost per GB, and to a lesser extent access time. All other things being equal, most users will choose the lowest cost per GB. However, they're willing to pay a few multiples of that for much lower access times, especially if the total cost with a capacity they can live with is still under $100.
The bottom line here is SSD manufacturers seem to be focusing primarily on decreasing the cost per GB. That's hardly going to get users to flock back to spinning disks. In fact, I'd say nowadays unless your storage needs are an outlier there's not much reason to go with spinning disks. That's only going to be more true in the future as SSDs come down in price per GB, even if their performance remains flat. The way I see it we'll end up with two possible scenarios. One, the focus will be solely on decreasing SSD cost per GB. This will mean much larger, cheaper SSDs but STRs will remain flat and access times may even increase. However, access times will still be an order of magnitude or two better than HDDs. So long as cost per GB is similar to HDDs, or not much more, nobody will want HDDs, except maybe in enterprise bulk storage where every penny counts. The other scenario would be less of a focus on decreasing cost per GB to the extent of all else. SSDs might continue to cost a few multiples per GB of what HDDs do, but they will offer access times three orders of magnitude (or more) less. And even with the latter scenario, cost per GB will still decrease, just not as aggressively. This will mean larger capacity SSDs at the sweet $100 or lower price point. Again, I'm not seeing people currently using SSDs flocking back to HDDs. There probably wouldn't be as many new SSD adopters in this scenario, but lots of people with 1TB or lower storage needs will flock to SSDs as their sole storage solution. Those with larger storage needs might have an SSD for the boot disk but HDDs for bulk storage.
The fact is other than STRs, HDDs are NOT getting any faster, nor can they get much faster. Their sole selling point is low price per GB. In the unlikely scenario SSD performance got so bad that SSDs matched HDDs in terms of access times and STRs, that still doesn't mean a mass return to HDDs. Rather, it would mean SSD manufacturers pulled out all the stops lowering cost per GB, with the end result that SSDs cost the same or less per GB than HDDs. End result, HDDs still lose. The fact is HDDs are a near obsolete technology. HDD manufacturers have already used most everything in their bag of tricks. The few things left, most of which solely increase capacity, don't even lower cost per GB by much.