Since you asked… if they bring back Firefly, then they have to deal with a fan base with views. The browncoats aren’t going to take too kindly to the suits urinating in the mix again, and the suits don’t want to deal with a Joss Whedon, given that he would be in a distinctly superior bargaining position for it.
Besides. No Wash. No Shepherd Book. That’s a hard thing to face.