Will we still have the gift of the Holy Ghost in the spirit world after we die?
I do not doubt that we will continue to enjoy the Gift of the Holy Ghost in the spirit world. When a faithful Latter-day Saint sits as proxy for a deceased sister, she is both confirmed a member of The Church of Jesus Christ of Latter-day Saints and given the Gift of the Holy Ghost. The Holy Ghost justifies and sanctifies us (Moses 6:60 and Alma 5:54). Any unfinished portion of this work will have to get wrapped up before the resurrection and the Spirit will be key in this process.