That has been the case since the hard drive crisis from the end of 2011. Well, SSDs stagnated or even went a little up over a 1-2 years period a few years back but now they're back in full swing. If this continues (which isn't a given, I'd say it's 50/50 chances) it'll be hard to justify spinning rust (all the "but but but unpowered SSDs can lose data in as little as X time" aside).
Yea, good luck with that, the formerly japanese Verbatim is now just a label for some Taiwanese/Hong Kong generic manufacturer, and if before there were some discussions about the BD M-Discs not being worth it and being mostly the same process now they don't even bother to use the MILLEN metadata, the difference being only on the box label (and price). What's worse some people reported some really bad quality issues (like 50% failures). So nope, you'll need to stick with the mainstream.
Pray that we at least keep this perk where the discrete storage is something common and cheap, and not some oddity like any of the dead formats or something reserved for Enterprise use with crazy prices (think tape). Already most people are using just what they get in their devices and that is morphing into stuff soldered into motherboards or even included into SoC (think CPU, but with more functions, but only one chip). And very often it's even encrypted and you can't get access to it ...
I don't think hard drives are going away anytime soon. Seagate just releases their dual actuator drives to market recently so not only are hdds not going away but they're still actively being innovated and improved upon.
For what it's worth, we're coming off of the bottom of a bust cycle in the NAND flash space.
The OP's graphs basically capture the NAND market from the previous boom through the current bust. So from that specific perspective, SSD prices have been dropping like a rock. The only catch with that window is that it fails to capture the cyclical nature of the market - and thus fails to illustrate how SSD prices go back up.
In practice, SSD prices have hit their lowest point. They are going to rebound here until the next bust in 2-3 years.