expansion main character: Male or female?

[Eiyaya]

Basically, i mean who the story going to evolve around mainly

Let's take a guess.

I say Female again.

looking at FFXI,
Rise of the Zilart: i am pretty sure Lion was... but it was more a group-like.
Chain of promethia: prishe (female)
Treasures of Aht Urhgan: Nashmeira (female)
Wing of goddness: No idea, i haven't play too far but i assume lizette?

then you get, that boy, moogle, and shantotto.

The other 3 are just new area, don't think there is a story.

[Dromox]

Knowing SE probably some boy under the age of fifteen.

[Eiyaya]

or some girls under fifteen.

i don't think they are all lolicon,

[Kilta_Firelotus]

There really isn't main characters. Just groupings. Technically speaking your the main main character well in your CS.

And there is an abyssea story line. Abyssea is the other universe hinted about in treasures I think it was. Inoder to get the story you need to see all the areas kill all the bosses/mini bosses then you can enter walk of echoes. Its a mini story.

[Lusavari]

You forgot a lot of Important characters. Along side Prishe, you had Ulmia who as a unique character, and Selh'teus, not to Mention Tenzen and that Galka I can never remember... And Nag'Maloda and Esh'natrl.

Then in ToaU your partners were Nashmeria and Prince Luzaf.

In WotG your partners were mainly Lilisette and Cait Sith, but you also had Five Moons, Zeid, Volker, Nickolas, Lehko, Rokbel-Akbel, and all the Young Griffons. So you ended up with a TON of partners. Unfortunately, as awesome as Adelheid was, she got left in the dust, especially after he adventure as a volatile escort.

As for the Add-on characters you're thinking of, you have Young Aldo, Belle Shantotto (who's actually just as evil as Domina) and my personal favorite, MY Moogle. Took'em way to long to work our personal moogles into the story...

Anyway, as for XIV, the major characters will come in groups, as they did in XI.

[Corrderio]

Pretty sure the "main" characters in the main scenario will just be you and your NPC.