I'm sure everyone has seen this by now, but the assembled the
Avengers cast on stage last night during the Marvel Studios panel. Renner is indeed playing Hawkeye, and Mark Ruffalo is taking over as Bruce Banner/Hulk. Pic (and details) at the linky, but it sounds like the following actors were there:
RDJ (Tony Stark/Iron Man)
Chris Evans (Steve Rogers/Cap)
Chris Hemsworth (Thor)
Scarlett Johannson (Black Widow)
Clark Gregg (Agent Coulson)
Samuel Jackson (Nick Fury)
Mark Ruffalo (Banner/Hulk)
Jeremy Renner (Hawkeye)
Pretty good lineup, I wonder if they'll be adding anyone else in the next couple years or not (like Wasp or Ant Man, who I think have been rumored off and on).