Buy any bubble memory lately?
I have a book from the early 90s which goes over some emerging technologies at the time. One of them was bubble memory. It was supposed to have the cost per MB of a hard drive and the speed of RAM.
Of course, that didn't materialize. Flash memory outpaced its development, and it's still not quite as cheap as hard drives or as fast as RAM. Bubble memory had a few niche uses, but it never hit the point of being a mass market product.
Point is that you can't assume any singular technology will advance. Things do hit dead ends. There's a kind of survivorship bias in thinking otherwise.
I'm quite aware of the history of the field, thanks. It's had a lot of cycles of fast movement followed by a brick wall. You can't assume it'll have a nice, smooth upward trajectory.