Not much is known about the as-yet untitled sequel to Star Trek Into Darkness except that it has an entirely new creative team behind it, as director J.J. Abrams and writers Roberto Orci, Alex Kurtzman and Damon Lindelof busy themselves with other franchises. We probably know who's going to play the villain, however, and that's Idris Elba.
News of Elba's involvement comes from Variety, whose sources say that the actor is in "early talks" (Hollywood speak for "unless we disagree over contract it's a done deal") to play the lead villain in Star Trek 3. An official announcement might not be far off, though it could always go the way of Benicio Del Toro declining to play the role of Khan in Into Darkness (the role subsequently went to Benedict Cumberbatch).
Returning cast members include the full bridge crew of Chris Pine, Zachary Quinto et al., including Simon Pegg, who shares a writing credit with Doug Jung for this installment. While primarily known as an actor, Pegg's writing credits include Run, Fatboy, Run, and, of course, all three films in the Cornetto Trilogy, Shaun of the Dead, Hot Fuzz and The World's End, so we can at least count on the film having a great sense of humor and some awesome action sequences.
There's no solid information on who exactly Elba will be playing, or, indeed, what. Rumors of Klingons forming the main obstacle of the third film have been cropping up since before Into Darkness hit theaters, but given the changeup in the writing and directing teams, it's really an anything goes situation. The Klingons were certainly well established as antagonists in Into Darkness, but Elba doesn't seem like the sort of actor you hire to swagger around spitting out harsh consonants (not that it wouldn't be fun to see him try). Of course, the Star Trek universe seems to have no dearth of surprisingly erudite, and therefore more threatening, Klingon leaders (like Chang and Chancellor Gorkon in The Undiscovered Country), but there's plenty more options for Pegg and Jung to choose from.
Elba would make a fine Romulan, for example. The different timeline of the new Trek films could be used to allow the infamous Borg to show up quite a bit earlier than they otherwise would. There's also plenty of grist, in this writer's opinion, in exploring the way in which Vulcans are attempting to rebuild their culture and heritage after the destruction of their home world and much of their population, and the conflicts that could arise there. In any case, let's hope that Pegg, Jung, and director Justin Lin can bring fans who were irritated by Star Trek Into Darkness' lukewarm reveals and plot holes, not to mention the sexualization of its female characters and the whitewashed casting of its villain, a movie worth getting excited about.