Wholly dependent on Microsoft. So far, they didn't say anything apart from indicating last year that they don't have immediate plans to do it.
Not wholly, surely? As an OEM, Apple would need to provide drivers. Given that their system isn’t an off-the-shelf SBBR/ServerReady ARM64 device, that’s going to be a not-insignificant amount of work that isn’t Microsoft’s responsibility.
Seeing as the Asahi Linux project has had to reverse-engineer pretty much everything, I don’t see how Microsoft could be totally on the hook.