I don't know if this is even a debate but fairly sure Tracy lives based on Greg Beeman's blog; he mentions this whole thing about saying goodbye to Brea Grant however mentions nothing about Ali Larter, leading me to assume she is not gone.
http://gregbeeman.blogspot.com/2009/03/episode-20.html
http://www.9thwonders.com/Greg-Beeman/
Fairly sure we already had confirmation that she was not going anywhere but I thought I'd add this in.
Possibly Tracy is dead and Barbara is coming in but they also said they wouldn't be introducing Barbara...