The fine folks at Ropes of Silicon talked to Buffy/Angel/Firefly creator Joss Whedom at Comic Con.
In the interview, Joss talks about his now-dead Wonder Woman but also about Serenity (Special Edition coming out Aug 21st) and the chances for another film in the series.

According to Whedon, Serenity ended up being fairly profitable with the DVDs. The studio approached him to put together a special edition because the stripped down version has sold so well.
The interviewer then asked about the chances of a second movie being made:

ROS: So give me hope for a Serenity II

JW: Hope for it probably rests with this DVD.

ROS: Well I’ll buy one.

JW: Actually I will too, people ask me why I would buy my own DVD and I tell them do you have any idea how awesome it is to buy your own movie?

ROS: So then you’re saying we’ve got a chance?

JW: Well it’s probably not being discussed in boardrooms right now, but the fact of the matter is if it makes enough money sooner or later they say “hey, this is money!” Also there are paradigms that are much cheaper, it doesn’t have to be enormous. But on the other hand I’m happy to say all of my actors are working very hard. It’s not the same situation where we all threw in for pennies because we had to finish telling that story. Now that situation might be harder to bring about.

So fans of Firefly should make sure to pick up a copy of the special edition version of Serenity. It has some pretty cool extras and, in my opinion, worth owning. I will put up a review as we get closer to the actual release date.