I'm really curious about Aimia and I hope to see more about in the fourth book. Have the Heralds or Hoid been there and will they reveal some stuff about it?
Brandon Sanderson (paraphrased)
Yes, the Heralds have been there and yes, Hoid has been there. However, I don't think there will be info about Aimia in book four, but in a novella I'm planning to write, like Edgedancer. The story will be about some characters travelling to Aimia.