(This is a word for word section of something I sent to someone else, but I'll repeat it here.)
There are between 4 and 6 episodes left of season 2 (most likely 5), and with this teaser of the next episode, it looks probable that this will be the last season, that is, if the series is going as it seems. A 3rd season has neither been confirmed nor denied at this point.
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Now, on one hand, I don't want the show to be unnecessarily stretched out a la SpongeBob, The Simpsons, The Fairly OddParents, etc. In fact, even just halfway through season 1 I thought what they'd done so far was a lot for one summer. But it seems like too many things just got started in season 2 for it all to come to a screeching halt. So many characters who previously lacked development now have something to them and now may only have 5 episodes left to do anything else. Plus, aside from all the serious and mysterious aspects of the show, I just like the characters and the setting. I want the show to have more time than it looks like it has to just be a kids' show. What some call filler episodes can go a long way, and besides, by some people's standards now, most of season 1 was filler episodes. Now, I don't think the show needs any more than a 3rd season, but I'm not ready for it to be over this soon. If it is, I have faith that the team will wrap it up nicely, but it will still be sad to see it go.

Two seasons is still pretty short. Even Spongebob went a solid three or four seasons (or even more depending on who you ask) before the rot kicked in.