So here are some interesting quotes from an interview with Vaughan here http://www.comicbookresources.com/?page=article&id=50441
"I don't want to say anything about #18 yet, but the six issues after it are going to be very, very different from anything that's come before. It's a story about money, among other subjects that terrify new parents."
" We're already hard at work on #19, and it's a doozy. You're either going to think it was totally worth the wait or cancel your pull-list subscription on impact."
"Fiona and I get option offers all the time, but I don't think the technology or financial model exists yet to realistically make "Saga" work as either a television series or a feature. I'm certainly open to being proven wrong though, especially if Paul Thomas Anderson is looking to adapt a pervy space fantasy for his next project. For now, I like comics way more than film and TV, so I'm happy for "Saga" to remain nothing but a lowly funny book."