Yeah, for a minute. Thor's had, like, a whole freakin' day.
Seriously, though, he's resurrecting his race one by one, he's no longer alone, and he'll have three of his closest friends back once the Warriors Three return. That's gotta at least warrant a smile. The only way it'll be okay if he remains grim through the Warriors Three's return is if JMS is saving all his smiles and happiness for the outpouring of emotion Thor must feel when Sif returns. I say "must" because, given the history between the two, it's a ****ing necessity to Thor's character that he be deeply, deeply emotionally affected when she returns. She is the love of his immortal life, after all.