Maybe I completely misread something about a month back, but I swear I heard somewhere that Cataclysm will introduce a feature where you can finally make an alliance with other guilds. As in, the guilds will show an alliance with one another instead of merging, allowing both guilds to be linked yet independent.
Let me know if I'm wrong about this, as I have a friend's guild I'd like to alliance with mine. If it doesn't exist, I'd love to see this feature in the future.