Will it (Or should it) be made? I'd say probably not. You'd have to really do something extraordinary to be able to make money with it: You'd need to make an adaptation of a TV Series which actually draws in people who never heard about the series in the first place. Either that or you'd need to make a niche game about some tiny chunk of the universe (Examples have been mentioned: A ship captain simulation game, a trading company simulator, a space warfare strategy game...), and you'd probably realize that having the IP slapped onto it would be hindering rather than helping.
Firefly had, overall, amazing storytelling. People mention the characters, but that is only one corner of the triangle of good storytelling, and Firefly had all 3 corners: Character, Action and Environment.
Example: Jayne is a fun character, yeah. But Jayne fixing up one of his old messes in a town full of people who think he's some Robin Hood character is amazing.
If you want to recapture the show in any way, you'd need to reproduce that. What this means is having the crew of the Firefly as the main characters, the kind of story you saw in Firefly, and the environments from the show.
To be honest, the first thing I thought of when considering how to adapt Firefly was Red Dead Redemption.
- Set the game between the series and the movie (All the crew are still there, and maybe explain how Book set that settlement up, and why Inara left the crew).
- Create several (Obviously smaller) "Open worlds", linked together by the Serenity (Hop in there and fly to another world). The Serenity itself is, of course, entirely modeled, explore-able and there's content in there. It is, after all, the most important environment in the setting.
- A Main Quest and Side-Quests you can do at your own pace. All of them keep with that "trying to make ends meet" theme from the show (No getting fabulously rich and sticking a big honking cannon on the Serenity).
- Open-World content enabling you to just break into Alliance facilities and wreak havoc or some such (Instead of enabling you to go on rampages on towns and all that).
- The strong narrative and character interaction that has already been proven to be possible in this genre.
On the hands of a very good team, and with an amazing budget, I could see this happen, seriously. But would anyone sink the kind of money needed to create an Open World game into this IP? I don't think so.