Umm.. let's not get carried away here.
=p You don't know how much I disliked that helmet, not to mention that was our very first impression on Halo 4. But, obviously I was over-hyping the novelty of this information.
I'm gonna throw out a wild guess that there is no set default armor, and when you start the game you'll get to make a choice between a few of the helmets and other armor pieces we've seen so far. (probably totally wrong, though)
Its a big possibility, but I think there should be a default Spartan IV armor set (think about guests players); Spartan III had it, even if they didnt used it.