I'm in. I love the "dark Tauren," and would love to see more from them. Plus, while we've seen plenty of troll instances, Cocles says we haven't seen a Tauren instance in the game (and all we can think of is good old Mr. Smite). And we haven't really heard from the Grimtotems since that whole issue with the spirit beast taming. It'd be nice to fight some cows for once.
There's lots of lore to mine there, too: Magatha is the reigning matriarch of the clan, and not only is she buddies with the Forsaken (obviously there's been something happening with them during Wrath), but she's rivals with Cairne Bloodhoof as well. It would definitely be interesting. Of course, this is all speculation -- we aren't sure that there will even be an instance in Thousand Needles, much less that it'll be Grimtotem based (the whole place is getting flooded, so anything could happen -- maybe the Naga will get a "fin-hold" there). But the idea of taking on the Grimtotem again seems like fun.