I don't think this will be at all controversial. Brett suggested, and there was no disagreement from the PEP editors, that plain text PEPs be deprecated. reStructuredText is clearly a better format, and all recent PEP submissions have been in reST for a while now anyway.
I am therefore withdrawing[*] PEP 9 and have made other appropriate changes to make it clear that only PEP 12 format is acceptable going forward. The PEP editors will not be converting the legacy PEPs to reST, nor will we currently be renaming the relevant PEP source files to end with ".rst" since there's too much tooling that would have to change to do so. However, if either task really interests you, please get in touch with the PEP editors.
it-only-took-15-years-ly y'rs, -Barry (on behalf of the PEP editors)
[*] Status: Withdrawn being about the only currently appropriate resolution status for process PEPs.