[1] https://www.reddit.com/r/intelnuc/comments/7ga2q9/skull_cany...
https://www.ifixit.com/Teardown/Apple+TV+4K+Teardown/97511#s...
At least since it's not a handheld touchscreen device, you can take it apart and replace stuff. It even uses Torx screws! But there's not a lot of discrete parts here, just the power supply,the motherboard, and the fan.
Once upon a time the Mac Minis would have let you replace the RAM or disk, but I'd expect it to look like a similar similar power supply + motherboard + fan in a box.
Minis a few years ago had a quad core processor option and a lot of people have been disappointed by its absence, making the current generation objectively worse than previous ones. I don’t think they’ll pass up the option to put it back in, IIRC it was something to do with their choice of Intel’s processor families that got it dropped in the first place.
It's not like Apple's going to make the new Mac Mini three times the size it needs to be and stuff a bunch of 3.5" HDD bays in for people who want to use it as a file server.
Smaller with fewer components and everything soldered/glued together is a cheap way to build smaller and cheaper at the cost or repairability, and Apple clearly doesn't care about repairability. They've said that the Mac Pro redesign will be more modular, but I don't see them doing that here.