So with the fact that Shiro was involved with what Xyclops did made me have a thought. Could it be something Apocalypse eelated. Cyclops did have him in his head for a long time and Shiro was a horseman. Not only that but didnt an interview say this was a more classic Poccy compared to Blood of Apocalpse and other recent appereances. If somehow part of the Poccy was still in Cyclops that would be a great way to have Cyclops "die" by something like Poccy taking over his body, or Ctclops giving it to him having fallen under the idea of mutabt survival.