While the question of which enemy Superman will face in Man of Steel was put to rest on Sunday, another big superhero-movie mystery remains: Who's the villain in The Avengers?

Rumors began as far back as July 2009 that Earth's Mightiest Heroes would become embroiled in a conflict between the militaristic Kree and the shapefshifting Skrulls, whose histories are intertwined with the major players in the Marvel Universe. The speculation reached a fevered pitch last December, when a New Mexico newspaper reported the Joss Whedon-directed Avengers would pit the team against the two alien races -- a claim that Marvel sort of dismissed.

Attention then seemed to focus on the Incredible Hulk and/or Loki, in a storyline perhaps inspired by Marvel's The Avengers #1. But in a sizzle reel shown last week at CinemaCon, Mark Ruffalo reportedly indicated the Hulk will be a hero rather than the catalyst that brings the team together.

That leaves us with the god of mischief, right? Not so fast.

The Daily Blam! reports that, at Kapow! Comic Con in London, Thor co-star Tom Hiddleston "hinted strongly that he is not slated to be making an appearance in The Avengers, contrary to recent rumblings Loki will be the focus of the superhero film's troubles."

Of course, that could just be a feint (after all, Man of Steel director Zack Snyder at one point characterized Zod's inclusion as "just a rumor") But it's looking more likely that the Avengers are heading toward an old-fashioned intergalactic brawl -- the kind of large-scale action a lot of fans were hoping for.

The Avengers stars Robert Downey Jr., Chris Evans, Chris Hemsworth, Scarlett Johansson, Mark Ruffalo, Jeremy Renner, Samuel L. Jackson and Clark Gregg. It opens on May 4, 2012.