I'm sure if any of the large corporations depending on legacy hardware would get together and pay people to make the necessary forks, 6 months would be feasible. Practically, they won't, though.

I see the deadline more as a "expect breakages in weird unofficial Debian downstreams that were never supported in the first place" or "ask your weird Debian downstream maintainer if this is going to cause problems now". It's not that Debian is banning unofficial downstreams or semi-proprietary forks, but it's not going to let itself be limited by them either.

And who knows, maybe there are weird Debian downstreams that I don't know of that do have a working Rust compiler. Projects like Raspbian are probably already set but Debian forks for specific boards may need to tweak a few compiler settings to make compilers emit the right instructions for their ARM/MIPS CPUs to work.

I only find the message passive-aggressive or insulting if you're of the opinion you're entitled to Debian never releasing software that doesn't work on the Commodore64.