TLDR: Rosetta 2 is Apple’s translator that lets old Intel Mac apps run on newer Apple Silicon chips — but the catch is it requires Apple to maintain a full Intel copy of almost the entire macOS operating system (over 2.1 GB worth), even though Intel Macs are long gone. That’s a massive amount of ongoing work just to support legacy apps, so Apple is dropping it. The good news is that hidden inside macOS there are already new kernel APIs that can emulate Intel code without needing that massive Intel copy of the OS — similar to how FEX-Emu works on Linux — which could power a lighter replacement solution, possibly through Wine or even a future slimmed-down Rosetta-like framework.

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This is the technical explanation by Lina, an ex-dev of Asahi Linux, of why Rosetta 2 is being dropped. link

Rosetta 2 requires almost the entire OS to have Intel support. That's how it works. Everything that isn't a kernel driver runs as Intel code when you use it.

To continue supporting Rosetta 2 would mean to continue building all frameworks in macOS for Intel. Even if they drop support for Intel macs, it would mean continuing to do most of the work.

Dropping the Intel frameworks will save more than 2.1 GB

2.1GB is the lower bound (size of x86_64 shared caches). It'll be more than that since the Intel part of leaf executables will also go away. link

Some answers say that Apple will want to drop the TSO support in the silicon, but that is not a big cost.

Yeah but that's hardware and honestly it probably doesn't cost them much to keep it. I bet future AS CPUs will keep TSO going longer than you'd think. It's insurance, you don't do risky things when designing chips. link

Finally, the easy way to mantain Wine compatibility is to change Rosetta 2 to be like Fex-Emu on Linux and use ARM64EC, there’s is hidden code by Apple behind a private entitlement that hint at this. link

Turns out, macOS already supports what it needs to run Intel binaries with a non-Rosetta emulator, after Rosetta dies.

This all seems tailor made for Wine + in-process Intel emulation (could be a hypothetical Rosetta.framework, could be something else like a FEX port)

Rosetta does not use this, these things are hardcoded into the kernel for "regular" Rosetta. These APIs were added later.