That was kind of overdue. The project started five years ago while massively overpromising.

They should perhaps have kept it in a separate branch back then, but now is the next best time.

CPython's selling point was that it is simple, fast enough with C extensions and the code was accessible. Complicating the code base for occasional 50% speedups (and regressions ...) just isn't worth it. There are so many other languages that fill that need.

Now, I hope that the PEP does not overpromise again and is accepted because of Instagram pressure. Instagram can keep its own JIT fork or switch to PHP, Go or whatever.