As reported by E! Online (via Superhero Profiles), Ali Larter will be returning for Season 3. The big explosion may have killed Niki Sanders (maybe not, you never know), but Ali will be returning as Tracy Strauss. No word on what the deal is with that character yet.
On a side note, check out the poll on Superhero Profiles. It asks “Will Ali Larter be a “hero” or “villain” for season 3?“, then gives the choices of “yes/no” rather than “hero/villain”. Oops! I told them about the small goof a few days ago, but they haven’t fixed it. However, 13 people have voted on it, even though they have no idea which answer corresponds with “hero” and which one with “villain”. 
