As the Night King became the unexpected second dragon rider, Game of Thrones put all the pieces into place for a shocking finale with the fall of the Wall and also the continuing mission of the White Walkers in season 8.
Sure, Daenerys may still have two fiery steeds by her side, but with the blue-flamed might of Viserion under the control of the Night King, ‘Beyond the Wall’ was a key episode in the history of Game of Thrones lore.
Game of Thrones season 8 premieres in either 2018 or 2019.
However, while casualties were always expected, it didn’t stop the death/resurrection of Viserion being anymore dramatic.