The only chance I see of Tokka happening is if Suki's alive and they officially break up. If Suki is killed before that, Sokka is likely to give up love because he is a protector by nature, and is likely to blame himself again for the loss of his girlfriend. Though while I do ship Sukka, one-sided Tokka is kinda cute, and it's very obvious she has a crush on him, but not everyone ends with their crush in the end y'know?
And now to the important question, Kataang or Zutara? I will have to say Kataang, partly because Zuko already has a girlfriend, but also because it's obvious(Mostly on Aang's part) they like each other. Kisses DO count for something when they're enjoyed by both, and yes Katara did look sad after the kiss with Aang, but he was heading off to fight against the Fire Lord, she was obviously worried about if he would make it.
Question though, why do people call Sukka for George???