The big T is an ambitions choice for a second villain. Thanos doesn't play small ball--puny things like world domination. He doesn't even fit the trope of omnicidal maniac, because he isn't a maniac (I don't consider him maniacal since he can actually accomplish what he wants, and anyway, Thanos is no preening godling like Loki.). Although they'll probably take the omnicide route for him.
I was wondering if the whole first movie won't be revealed to have been a feint by Thanos...somehow, without Loki's knowing, he manipulated Loki into meeting up with the Chitauri. The fact that the head Chitauri was kneeling to him directly means that Thanos had the Chitauri directly sewn up as servants while this was going on. I mean, it wasn't as if the head Chitauri was meeting him for the first time. He was making a report. Thanos would figure he'd win either way this goes--he wins by taking out potential enemies if Loki and the Chitauri had somehow won (after which he'd have probably killed Loki, and he could).
Or, if he "loses," as happened, he knows that much more about his enemies from a distance, has lost nothing more than some easily replaced pawns, and is still rid of Loki possibly making any kind of future nuisance of himself.
