I liked the idea behind WoD garrisons, but not the execution. I really think that if they applied the same idea to a Guild Garrison, it would be more popular.
I like the socialization of being in a guild, but it's just missing that extra... substance. I'd love something tangible that we could all work together towards, and even meet and call our home.
On Alliance, I imagine a keep next to Stormwind that would have the guild flag on its walls (or vacant, if you're not part of a guild).
on horde, im imagining a new building near where the allied races building is