Not gonna happen, so it's a bit irrelevant. QEMU's architecture is fairly generic and it was never built for speed in the first place. Improving the speed of emulation is more about getting better than the current baseline of "10x or worse slower than native, and continuing to gradually get slower if we add features and don't actively try to work on performance". If we got to "3x slower than native" I would be really surprised.

Which isn't to say that you can't do better than 3x-slower under any circumstances, just that if you wanted performance you'd probably be better off starting from scratch with an emulator design that cared about performance and which was really clear about its use-cases -- eg "this is user-space only, not system emulation" and "this is only this very small set of host and guest architectures". QEMU does a lot of different things in one codebase, which makes it cumbersome to change anything and hard to put in optimisations or simplifications which might be valid for a specific host/target combination but not more widely.