that is a possible thing yes. As things are now with only about 5 or 6 active societies, creating private forums for them would be acceptable. But as game attracts more players and more societies are created, creating a separate forum for them would be a big issue for forum and database maintenance.
This would be a very convenient way of having all in one place, but it is my opinion that socs should arrange their own way of providing a good means of communication between their members