I don't get why everytime a "sci-fi western" comes up people suddenly think it's a rip of Firefly. Newsflash: Oblivion, Galaxina, the Wild Wild West (the good one with Bob Conrad and the crapfest with Will Smith) and about a half dozen other films and TV shows I've forgotten had been doing the SF western thing long before Firefly came along.
No question; but Firefly has kinda ruined the "overt" SF/Western hybrid. And that's as much about the treatment it got as the series itself. The way that whole thing went down, no TV network----especially Fox----can go near the concept without it bringing Firefly to mind for all concerned.
Ironically, if Firefly hadn't been as good, this would be less of a problem.....
All it means is that for the concept to succeed again, it either has to be done exceptionally well, exceptionally differently, or it just has to wait a while longer. The bar is gradually settling at this point, but it's still fairly high.