By no means am I expecting a Firefly return, but that does not mean we cannot have a spinoff prequel with browncoats or another aspect of the Serenity battle. If fans want it Joss will build it. Other than Summer Glau, Adam Baldwin, and soon Morena Baccarin with "V" what is the other cast up to anyway?
Fans DID fight for it. That's how we got "Serenity" in the first place. And frankly, that was an incredible achievement.
I think for most of us "Serenity" was a satisfactory conclusion to the story, so we are all willing to move on. There's no reason to force more out of it.