Game of Thrones Season 8 and Prequel ? | HBO Announcement

Here I discuss the HBO announcement of extending Game of Thrones beyond season 7 for at least one more season for a total of (at least) 8 seasons. Is this stretching it out too far? Also the announcement of a possible Game of Thrones / A Song of Ice and Fire prequel. What type of spin-off would you like to see? Discuss!