Oliver H. Olney, on August 27, 1842, reports he has heard from some members of the Church in Nauvoo that, if Joseph dies, Hyrum will be his replacement; also, there are rumors of a move to the Rocky Mountains.
Oliver H. Olney, Journal, August 27, 1842, in The Writings of Oliver H. Olney: April 1842 to February 1843—Nauvoo, Illinois, ed. Robert G. Moore (Salt Lake City: Greg Kofford Books, 2019), 155
They say if Joseph is gone God has apointed an other in his stead to lead us That is his Brother Hiram. Thus a door is opened for to lead them along step by step It is said that Joseph but the secret whisperins is that he is in the Citty of Nauvoo Amaking ready to start to the noted boiling springs amongst the Natives neer the Rocky Mountains.