For my two girls right now, if something happened to me, my mom and dad would take Bella and Zoey both. If I had another puppy/dog that wasn't from rescue my breeder may take the dog back, or my sister or parents. Everyone in my immeidate family (Mother, Father, Sister, and half-brother) are animal lovers, and my brother is espicially a dog person. I bet if something was to come up, he'd take Bella. If fact, he was going to take Bella when she was looking for a home before coming to me...
If something happend to all of us, like say we were on a family trip, and all died somehow, I don't know. We have 7 dogs, and 6 horses, and a pony, and a ton of goats and sheep. Goats and sheep probably to a friend of ours, and probably some of the horses too, and maybe one of the dogs. My aunt would probably take one. A close family friend would take one. The two oldies (Callie and Sasha) would probably be PTS if they were still alive. Morrie'd go back to his breeder... And Bella'd probably be SOL - sad as it is... But then again, my trainer might take her...
I've never really thought about what I'd do if my family wasn't there to take them. All I know is they wouldn't be sent to shelters.