The fact that the show so freely utilizes the concept of multiple dimensions and universes gives practically endless possibilities to its writers on how they can continue it, and they certainly have a lot that they can do if they want to make this season truly shocking.
But they should also keep in mind that many people were originally drawn in by the witty humor and good writing, not so much by a dark storyline. The writers could turn a lot of people away if they focused too much on the wrong aspects.
They definitely seem to know what they’re doing though, judging from everything we’ve seen in this show so far. They’ve handled the first season pretty much perfectly, and season 2 has been running very strongly so far as well.
The show is at the peak of its popularity right now as it’s managed to enter mainstream discussions very effectively, and people from all sides are now discussing the new episodes that have come out lately. This could actually be the perfect time to do something truly dark and twisted with the plot, and while we don’t know if the writers are planning something like that, it’s definitely something we would expect from them, given everything we’ve seen so far.