The brazilian Trek Brasilis website, the major Star Trek website in Brazil, posted in one of their articles a note about possible spoilers for Star Trek XII.
According to the article, a trusted source to the site revealed to them that the movie villains are the Klingons and that is NO time travel involved this time.
This is, of course, an anonymous tip from an unofficial website, so all things considered I'm not so confident about this rumor. However, Orci & Kurtzman have mentioned in the past that the Klingons were possible villains for the sequel, so who knows...
What do you guys think? I don't really have much of an opinion-- I'm not a huge fan of the Klingons generally, but I'm sure JJ & co. can do something innovative with them just as they did with the rest of the Trek 'verse. As long as the Klingons, if they are indeed the villain, pose a unique threat to the Enterprise crew that ultimately leads to kickass/heartbreaking character moments, that's all I really require.