They are a domestic animal.
Just to clarify some points, I'm not against the inclusion of the llama in concept, I'm against wasting a slot on something that isn't exciting or necessary. Presumably the theme here is South America. We can assume it's a broad theme rather than a more localised one (the Andes, or something to that effect) because I doubt we'll be getting DLC's forever more to cover all of the possible content. So if we assume it's South America, then the llama is perhaps the least interesting animal they could have possibly included.
We must also assume the pack will only have four animals. Before anyone gets all huffy about this assumption, it's based purely on deductive reasoning; the first DLC we got was reasonably priced for what they included (four animals, building set, campaigns/challenges), and so far we know in this next DLC that we're getting a new theme (some kind of temple ruins), so it follows that this will be the new building set. We can also assume we're getting new campaigns and challenges as we did in the Arctic Pack, so it also follows that we'll be getting four new animals (we won't know until the whole DLC is revealed, but this is the safest and most logical assumption based on the information we have about PZ DLC's).
So if one of the four is the llama, and odds are good another of the four will be the jaguar (which is better, we all want that one), then what about the other two slots? What can we reasonably expect here? Are we going to miss out on something great (giant anteater? Capybara? Spider/squirrel/howler monkey?) and end up with, say, the spectacled bear and the black caiman?
This is all conjecture and not based on any insider information of course, and I'm not saying I'm going to be right or wrong, but it does make me worried.