In my opinion think the stackables have some growth potential. One aspect is that these stackables with their input and output connections are still quite relevant. Also the minimalistic design is something that might intrigue some people. And (the best part imo) you can use them with either passive or active speakers.
The other aspect is that the footprint of the system is somewhat familiar to the more traditional HiFi systems. Beocenter 9300 and 9500 have somewhat an unconventional footprint so I guess it looks a bit unfamiliar to non B&O fans.
My main motivation for getting into the stackables is that they don't have any buttons and knobs on the front plate and are therefore much toddler friendly :). My toddler kept fiddling with the knobs on my previous vintage amplifier.
But yeah, this is like picking the right stocks in the market, it's hard to guess what the market will dictate.