>I'm not worried about this happening on PCs. All empirical evidence points against it. Hardware support in Linux has gotten (much!) better over time, not worse. Secure booting has been talked about for almost a decade and I still haven't seen any machines that require it.
Sure. But now it's required for ALL new PCs.
>Ever since the IBM PC became established, software compatibility has always been an overriding consideration in PC culture, fueled largely by vendor reliance on software lock-in as a profit driver (which requires backwards compatibility). Simply put, you can't lock down a PC too much without damaging software compatibility. I see no evidence that the historical emphasis on software compatibility for PCs is diminishing in any way. Even the latest 64-bit multicore Intel machines can still boot DOS 5 in real mode.
That was before the era of virtual machines. You can't run 16-bit DOS programs on 64-bit Windows anymore, for example.