I have been waiting for the 3.0 final to post this, but I noticed the same thing, so I'm ready to pose my question...... I noticed, starting with RC3, that while the version informaiton changed for spamd and spamassassin executables, the spamc executable still reports RC2.
It doesn't do that here:
thor:~$ spamc -V SpamAssassin Client version 3.0.0
Installed from tarball, not CPAN. Are you *sure* there isn't an old one floating around in your path?
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Regards,
Marco.