Reportedly Joss also said this at a convention in San Deigo -
"I don't consider the finale to be quite as open as some people have said," Joss confessed. "Let's see, Gunn definitely dies, and many things are possible. I don't intend to continue the series, I think that the series is over but like I said we're talking about TV movies, we're talking about different venues. I would like to see what happens to those characters in some format we just haven't had a go on what that happens to be yet. But trying to bring back the series I think that it's sort of beyond that now."
http://www.cityofangel.com/behindTheScenes/bts4/sdcc04_3.html
Later there was another reported remark from the Kerry fundraiser -
"He was asked again about the Ats cliffhanger and he repeated that the message was that you have to keep fighting…
But he went ahead and said (I think he was being flippant):
Gunn dies (groans in the background…I think J August Richards was there)"
http://whedonesque.com/?comments=5162