Thor is smiling, there is hope in his eyes that he could fight alongside Loki again. No matter how many times these two had argued in the past Thor was always looking out for Loki and Loki looking out for Thor.  That’s why at certain confrontations he was insisting that Loki not go into battle. Thor wanted room to go completely berzerk. 

If Loki was ever injured, Thor would go apeshit. “No! None lay hands on the family of Thor so long as he commands the thunder!”

( If you’ve read the MovieVerse Comics of these two specifically you’d know they had quite the adventures. ) 

Loki is lost though. He’s really mad at Thor for the way he feels and he’s mad at himself for it too.

I hope…that they can get back together, they were a very very good team.  And regardless of how some feel of sorcerers on the battle field – Loki is a warrior through and through, Thor knows that and mourns.

Loki’s destiny is a dark and twisty road, who knows…