I don't think it really is as much of an issue of SciFi airing it or not. The actors are no longer under contract. With the publicity and acclaim all of them have recieved, they likely won't have problems finding other work. Then it is a matter of being able to get all of them at once. I'm still optimistic we will see the second half of the season at some point. I doubt any of the actors/crew are going to want to leave the story unfinished. I would hope that we at least see something by next Spring/Fall.
I think they'll come back. They also don't need to get everyone at the same time - depending on what needs to be filmed, they only have to get a few characters' schedules aligned and can just film things out of order.
You would think, but production doesn't work that way.
I'm not trying to be negative, believe me, BGS is one one my favorite shows made by one of my writing heroes and I want more than anything to see it finished. It's not impossible for the show to come back, but a lot of minor miracles have to fall in line. As soon as I hear anything on the positive side (which me and three of my buddies who also have contacts or work with/for the Sci-fi channel are checking into,) believe me, I'll get it posed ASAP.