To be honest I'm much more excited about Starlight Glimmer making an appearance. But this...this alicorn is a little disturbing. How many alicorns are we going to get, anyhow!? Geez, this is getting ridiculous. And the premiere is only four or five days away. Speaking of which, is anyone going to watch it right as it comes out (not that I will)?

I like how we went from two Alicorns to five. However, to be fair, she was birthed from Cadence. Then again, Cadence "ascended" as it were. So.. I have no idea.

However, I believe in the Journal of the Two Sisters it is confirmed that Celestia and Luna were born rather than ascended, and that they were raised by other alicorns. So, either they are the "last of their race" and normal ponies can be artificially ascended, or... I have no idea. However, the answer to your main question is, both.

But personally, I subscribe to this headcanon about baby ponies' abilities.

I mean, we don't know how Cadence, Luna, and Celestia became alicorns, so it's fair enough to assume that they could've been born as such.

Besides, we've seen Pumpkin and Pound Cake were able to fly and use magic when they were babies, but not very well. I'm not too bothered by it, to be honest.

We have yet to know if the sisters were born with the whole package or not, unless I'm missing something.

Also remember that MLP is essentially a glorified commercial, sense takes backseat to whatever the heck Hasbro wants to sell at the moment.

(But there were toys for the character since what? Season 3?)