And I'd really like to see a CPython summit happen at some point. There's so much interesting stuff going on in that area that it's worth getting some people together to move these things forward.
Yes, a CPython runtime summit some year would be interesting.
I don't see why CPython-specific stuff can't be discussed on the language summit. After all, everyone can be not interested in a topic X or topic Y. I would be even more than happy to contribute my knowledge about building VMs w.r.t. CPython implementation as much as I could.