How do you think the Toa Nuva will earn back their elemental powers?

Well clearly they'll take back the symbols. How though we really have no idea but we know it'll involve the Vahi.

Take em back? Oh duh...silly me...

They most likely will have to go through the Kal first.

Moving to theories...

Probably steal them from the Kal, while using the Vahi

after the kal saga they will polpley grt thiere powers for good.

I personally think they'll get their powers absorbed into them so if another enemy wants to fight them,the rahkshi, they won't have that weakness.

I think Tahu will use the vahi to slow down time so much that he can run around really fast and grab them back. Then he gives them to Pohatu to rush back to each village and put in their place. Of course Pohatu could do the first part, too.