Nowadays there are 8 kingdoms, I assume all of them are going to pick during Domain Selection rather than break their community and look for specific tribe.
I think we need more info about each tribe before see official preferences. Know more about each biome and the variety of architecture could help people decide. The only think setted is there will exist one double kingdom through Eu, so it could have more than 2 main tribes.
Leaders and Headers are hidening their choise in order to have any advantage at Domain Selection. Also, many big groups are waiting until that period to choose the better pick option.