Nope, not doing one.

Bungie's latest Mail Sack is up. Here's a highlight:

MastaSin In Destiny, can we play as the aliens or are we locked to the human race? And if we are, why are we locked to the human race? What's the reason?

Deej Not all of the aliens in Destiny are evil, just like not all humans are good. We’ve barely scratched the surface on the character and customization options you’ll have access to in Destiny, but we’re not going to dig in any deeper today.

I believe one of the early IGN stories seemed to indicate that players would only be humans, but this seems to cast a bit of doubt.