They confirmed there would be 4 new guild halls, that's about all that's known at this point. This was in an earlier FAQ about Factions on their site:
"4 new Guild Halls, new Guild Emblems, and a reworked Rating System."
1 is going to be a assassins themed hall
1 is going to be a ritualists themed hall
1 is goign to be a luxon themed hall
1 is going to be a kurzick themed hall