The tide does seem to be turning that way, though I do think it will be possible to buy general purpose computers for the foreseeable future.
Also as a minor counter point, the only reason Asahi is even possible is that Apple explicitly designed in support for booting other operating systems into the M-series chips. They certainly could have locked them down just like they did the iPhone and iPad, but they didn't. That was a conscious choice according to the Asahi folks.
So while they may not be sharing technical documentation/drivers or otherwise making it easy on the Asahi devs, even the famously "walled garden" Apple seems to have explicitly not restricted their new line of computers in the way you're describing.