> The only issue is software

So like half the thing then? It is kinda important bit if you actually want to use the thing.

Plus in my experience many of "the hardware is ready we just need software to catch up" issues turn quickly into "uhm, oh, we have several hardware issues but hopefully the software can work around them eventually".

> But I can't imagine it's impossible that one of the usual SBC-SoC manufacturers would finally start doing proper upstream Linux kernel work.

One can always hope. After a while one might think that the reasons they are unable to grow up to the task is structural.

Either way the reasoning "somebody one day might start doing what Raspberry Pi is already doing" is not as damning as you make it sound.