Marvel Studios today announced that production on The Avengers had begun (director Joss Whedon let the cat out of the bag with an earlier post on his blog, see “Filming on ‘The Avengers Begins”). Along with the announcement, Marvel released the first (very unrevealing) set photo from the production, but more importantly noted in its press release that Tim Hiddleston and Stellan Skarsgard will both reprise their respective roles as Loki and Professor Erik Selvig from Kenneth Branagh’s Thor movie.

Marvel’s announcement appears to confirm spoiler-filled reports about the post-credit sequence in Thor, which have been all over the Internet since the film opened last Friday in Australia. So now we know that Loki will be in The Avengers, but will he be the film’s main villain?  Previous speculation mostly centered on a Kree-Skrull element in The Avengers (see “Kree-Skrull War in Avengers Movie?”), a concept that gained a little momentum when Upper Deck announced it was publishing some new Kree-Skrull comics in a trading card format (see “Upper Deck to Publish Kree-Skrull Comics”).

The Avengers opens just about a year from now on May 4th, 2012.  Marvel has shown an ability to run a pretty tight ship, but there are so many ways that news can leak out from a movie set.  How long will the identity of the film’s primary villain and the details of its narrative remain hidden?