What chance is there for the Saudi throne to skip a generation?

Abdullah is 86 yrs old, although he appears healthy. Crown Prince Sultan is 85 and away in Morocco convalescing for his illness. Prince Nayef is 76yrs old and reportedly suffers from Leukemia (and not so popular). Besides Prince Salman (73yrs), who would be next in line? What are the chances the heir would be from the next generation?