Specifically, PEP 617, which is Standard Track Accepted.
I want to correct some inconsistencies between the Syntax section and the meta-grammar shown in the Grammar Actions section. This would not change the effect of the meta-grammar, but merely make things consistent.
Beyond that, I would like to expand the meta-grammar, and the corresponding descriptions, to incorporate some new features. This would be accompanied by changes in the python/cpython repo.
Perhaps, this would be best served by a new PEP. However, I would want to see this new PEP be cited in the Developer’s Guide, and in PEP 617 itself, so that programmers would easily know about the extended grammar features.
We generally don’t update accepted PEPs (they’re historical documents). For new features, you can discuss them here (well, on dpo, not necessarily in this category).
Standards Track PEPs rarely make good long-term documentation. I would instead recommend that you look at lifting the meta-grammar into a page in the Dev Guide (assuming it isn’t already there, of course!.
This would be orthogonal to actual changes for new features, which as Eric stated, are best discussed as their own ideas (independently of the Dev Guide and PEP system).