My understanding matches AM. Perl 5.10 will not
be based on Parrot.
Instead, as announced by Larry last year, a normal Perl 5.10 will be released as well as Ponie 5.10 which will run on Parrot. If all goes well, Perl 5.12 may never get released, there will only be Ponie 5.12. If it doesn't go so well, I'd expect parallel Perl 5.12 and Ponie 5.12 releases. (Personally I'd bet on enough people not wanting to move that there will be parallel releases.)
Either way though, there is a clear distinction between Perl 5.10 and the version running on Parrot, Ponie 5.10.