Apparently Nightcrawler was the last piece of the puzzle for now; that's what Lariviere said he had completed just before the tweet:
Hair color for # Casting Nightcrawler done #Hair Color QuickSilver done . # X-Men Apocalypse # Shooting April 27.— Felix Lariviere (@Felix_Lariviere) April 22, 2015
Bryan Singer will direct X-Men: Apocalypse, starring Sophie Turner, Olivia Munn, Jennifer Lawrence, Rose Byrne, Oscar Isaac, Evan Peters, Michael Fassbender, Nicholas Hoult, James McAvoy and many more.
The film is due in theaters on May 27, 2016.