It does suck that another race can't be Druids. Right now we are limited to two races per side. Its better than the one we had before Cataclysm came out. Some people do however love Druids but want more choice. Right now however, I don't see any real lore that would allow another race to be Druids. However, there are some things you can twist around to allow it.
Orcs: Orcs have the ability to be shamans. They are in tune with the elementals and a bit of nature. However, I don't see them being big Tree huggers. They could probably have their lore twisted a bit to become druids, but I see them as to much as a brute force for it to really work.
Goblins: Just no.
Blood Elves: People are continuing to ask for Blood Elf Druids. In some sense I can see it, in others; they are to bent on magic to really look to nature for a home. This could be one of the ones that have their lore completely hellbent to become a reality though.
Undead: Unless they somehow count growing mushrooms on your rotting body....No.
Humans: While Worgen are technically Humans, I don't see Humans with their normal greed and un-trusting nature of things they don't understand; being able to commune with nature.
Gnomes: It would always be funny to see this. Gnomes in some sense may be able to use their intellect to figure out how to work with nature, but I don't see them doing it.
Draenei: This is one of the races I can see becoming a Druid. When you start off with them, you end up meeting a Night Elf and and work trying to save her and get her back to her people. They are very close to nature but more so followers of light. Their lore can be twisted around every which way possible to allow them to be Druids. However, a bear with tentacles on its face is a very scary thing to think about.
Dwarves: They can be Shamans, but it would take a lot of twisting for them to even be close to becoming Druids. After being a Tauren for about 6 years, I already have it implanted in my mind they are out to destroy the land with their constant digging and looking for riches. In AV they want to dig up the resources but the Orc Clan there is just trying to protect their home. So yeah..don't see this every happening.
In short, only races that even come remotely close are Blood Elves and Draenei, should they wish to allow another race to be Druids. I however am happy with two races being Druids and would rather see a new race an Expac or Two slipping in to the Druid way.
Anyway, I put a poll up. If you could choose a race to be Druids, which would it be?