All of those things you mention take advantage of the economies of scale of ARM production. They exist because a few years ago the basebands they're using were top of the line and were used in upmarket devices. They can buy an old baseband/board design, attach a screen and battery, and have a cheapo device for essentially zero development cost.

If RISC-V doesn't see the development for upmarket products it's not going to magically take over the downmarket segments. No one footing the development bill is going to selling $50 tablets.