I don't think that's necessarily a prerequisite. At least you could conceivably see demand for low-power, moderate performance Chromebook(-like) devices. For true desktop computing, yeah, I agree.

A fees dollars saved from not paying ARM will guarantee adoption in low end laptops, tablets and smartphones.

$100 Laptops, $70 phones and $50 tablets will be a big target for RISC-V.

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.

ARM could just start price-matching the various RISC-V vendors, making themselves the easier choice due to the software ecosystem

They would have to offer the core for free to the SOC designers.

The (good) riscv cores designs that implement the spec aren't free, it's the ISA spec that is free.

There are some open source riscv cores, but the paid ones make money for a reason