So as many of us who have played the beta already know, the wood elves of ESO can have horns/antlers sprouting from their head? Taking into perspective that we saw the same thing to a lesser extent in Morrowind, what do you guys think this is about and why can they have them?

There is probably a lore reason in their background for such a phenomenon. I have not enough knowledge to add substance, sorry.

Logically though, since not every Bosmer develops them they might either be an external result of some ritual/life state or ancient genetics that don't show for everyone.

This thread would have been so much better if titled, "Horny Wood Elves"

Haha, wow, why did I not think of that? Shame on me.

Some lore reason I am guessing, and while I would consider myself to know quite a bit about lore, I just don't know with this. most likely do to Morrowinds horns, as you said.

Maybe to reperesnt they are wild or something.

Bosmer have always had a bestial component to them. Have a look at http://www.imperial-library.info/sites/default/files/pge01_aldmeri_pic_02.jpg illustrations from the first pocket guide.

It's also a component of the wild hunt, a ritual that causes Bosmer to transform into monsters in large numbers when Y'ffre wills it. The antlers are not exactly a manifestation of this, but a sign of the same principle. In Khajiit myth (and Bosmer ones, which I think have more of an appearance in ESO) the Bosmer are the result of being fixed into elves in the Dawn Era. There is variation among the Bosmer in how "elven" they look, with some having more animal-like features.