This comes from Incredible Hulk actor Mark Ruffalo who tweeted the "Avengers is not being shot in 3D."
However, the same ("not being shot in 3D") can be said for Thor, which did have scenes converted to 3D.
I'm not sold that Marvel Studios isn't going to put The Avengers out in 3D. I believe Thor made a few extra bucks at the box office due to sales for 3D, so there's that.
Still, more and more people seem to be against 3D, as of late, so consider this a step in that direction.
Ruffalo also tweeted about wearing the Hulk Motion Capture Suit:
"Motion Capture is pretty good except the suit makes you look like a walking chinese checker board."
And most likely a comment about the new Avengers poster:
"I have to inform the wolrd that the Hulk may be completely bare assed in this AVengers."
The Avengers hits May 4th, 2012 and is directed by Joss Whedon, starring Robert Downey Jr. as Iron Man, Chris Hemsworth as Thor, Chris Evans as Captain America, Samuel L. Jackson as Nick Fury, Mark Ruffalo as the Hulk, Scarlett Johansson as the Black Widow and Jeremy Renner as Hawkeye.