J.J. Abrams' Star Trek was impressive, it was a fine balance of old and new, intricately weaved through a very strong storyline. The truth is you can simply not bluff your way through this kind of tested franchise because its history and identity is sacred, re-launching it was no small task, he, along with writers Alex Kurtzman and Roberto Orci have set the standard quite high for the sequel.
One of the major questions is who will be the villain? Here’s what Kurtzman said regarding that topic.
Starting at a premise of what you want to see and then working a story around it is not how we do it. You have to start with what is the right story. And that if you can say “That’s a story that Khan fits into”, that’s how you get to that. Not deciding on a menu list of items and then seeing if you can’t string them all together.
Introducing a new villain in the sequel is tempting because we now have this incredible new sandbox to play in. On the other hand, some fans really want to see Klingons and it’s hard not to listen to that. The trick is not to do something that’s been seen before just because you think it will be a short cut to likeability.
Finally, regarding the tone of the sequel, the pair said that it will be similar to the first film. Says Kurtzman:
The first one had dark elements, but was ultimately very warm. We’d hope to strike a similar balance [in the sequel].
And Orci adds:
Humor is part of the franchise and I think it’s critical, certainly to the Bones-Spock relationship. It’s definitely a big part of the Bones-Kirk relationship. So, I don’t see any world where humor doesn’t play a part.
Personally I don't think Abrams will bring in a new Villain, not after doing it in the first Movie. The obvious choice is as mentioned Klingons, but because of the "new" timeline there really is no constraints. Screenwriter Damon Lindelof is also involved in the sequel and he recently stated:
“We’re looking at a movie like The Dark Knight, which went one step beyond Batman Begins… It was really about something, and at the same time it was a superhero movie. We don’t want to abandon all the things that made the first movie work…but we also really want the movie to thematically resonate.”