king of nowhere (paraphrased)
Then I asked him about Jasnah in Shadesmar.
Brandon Sanderson (paraphrased)
He said that he still is not sure whether to include it in the book or not, but he most likely won't. The reason is that he fears it will lessen the impact of something that will need to happen later in the book. so, it implies some characters will visit Shadesmar and have some important adventures there, which Jasnah's story may spoil. he is looking forward to showing Shadesmar on Roshar; we saw it on Scadrial, but on Scadrial it is mostly uninhabited, while in Roshar there are all the Spren.