Quite a disappointment, indeed. However, I remember that in 2016, it looked like Yamaha wasn't going to introduce the expected PSR-E453. I even called Yamaha, and while I don't remember exactly when this was, I believe it would've been after the NAMM show of that year. Of course, Yamaha wasn't going to give out their product plans, and they told me that there were no plans for a PSR-E453 but that "something different" would be introduced later in the year. I even posted a thread here about it that I titled "Could it be? No PSR-E453?", but that thread is probably one of the ones that was previously lost when there was an issue with the forum and a bunch of threads were lost.
Well, of course, a couple months later, Yamaha DID introduce the PSR-E453, and the "something different" later in the year was likely the 76-key PSR-EW400 version.
So, maybe there is hope. Maybe Yamaha will still surprise us, yet.