Personally I think that Rumple’s future seeing abilities work like a give get type of thing. Kind of like the dark “force” that has taken over him requires that he can do nothing for free, which is why he always asks for something before he gives something(before the dark power will let him see whatever is being asked of him). For example he had to ask for snow and Charming’s child’s name before the dark force would tell him or let him see that that child would be the one to break the curse in 28 years. I hope that makes sense.