A mass renaming of ports would basically cause massive failures during upgrades (why can't any of my port dependencies activate during upgrade?) unless every single py-* port was DUPLICATED as a py24-* port and then made a non-installing dependent of the py24-* port (look in the SVN history of port abiword to see how we migrated multiple ports to ports with different names) I would leave existing python 2.4 ports alone for historical reasons, but use py[version]-* for all new ports.
You're right. So I would like to leave py-* ports *for a while* and treat them as deprecated ports, and user who installed deprecated ports would be warned by warnings like "py- ports is DEPRECATED, which means no update is made in this port. Please install py24-* instead. You're warned!" Luckily, python24 is a bit old (The current stable is 2.5) so I hope this would not impact so many users.