Unless I'm mistaken, we've not seen a single cutscene where the player character talks. 

Also, since gender is optional, they'd have to record all lines twice.

Probably. It would also give me a very good Chrono Trigger vibe if they keep the protagonist silent!

Probably yes.

Nope.

"– Some famous voices actors providing their voice as options for the avatar, will be announced on the Xenoblade homepage later."

http://nintendoeverything.com/xenoblade-chronicles-x-details-world-size-battle-system-gamepad-usage-and-more/

Yes and no.

It will be something where the protagonist doesn't talk during cut scenes or anything like that, but will still make sounds in battle and say stuff.

I know that even Fire Emblem awakening allowed you to choose the player character's voice but I just get the feeling that this game's story won't really focus as heavily on the player character. But I may be wrong about that, its just a feeling I get.

Maybe ...

If they do include voice acting it would be for gameplay purposes, not for plot ...

I wouldn't mind having voice acting removed from video games entirely.

I will say no

That could just be the things the character says during gameplay. You know, the techniques names, the sounds he makes while jumping...

I don't think the protagonist will actually talk during cutscenes. He will be silent.

I hate it when characters, and sometimes entire games coughZeldacough, are silent. It's not a 'creative decision', it's laziness and cheapness.