My Horde Shamans are completely capped out and I was pretty bored, so I leveled up and in the process of gearing out Alliance Shaman

It's hard to make anything else when you know what works - the xpac is swirling in many role defining changes for classes, another class could rise and become the ultra mega mega flavor.

I'd go with whatever you have fun doing, it's the most simple and effective way to make a decision I've found.