Ok Im gonna make a few key points here since I've always been adept at Language Arts lol
but if you look at how shu's void which I've dubbed the "King's Arm" is explained to do Gai states it "gather's everything and assumes its weight," by carrying the weight of others "strength, weaknesses, light, darkness... Everything."
If that be the case and I believe someone mentioned this before Shu more than likely has absorbed and seald within him the voids of the world and because voids are essentially the shape of one's soul and Shu could have in turn absorbed Inori's soul through the flower created from the reaction of her tear and the virus (for those not paying attention thats how shu uses Inori's Singer's Sword Void to fight Gai who is using Mana's Longsword Void). So in the end when Shu closes his eyes and is with Inori in spirit that could be from him having absorded her soul
Also as stated previously Yuu hasnt died he teleported away and the other guy Daryl wasn't shown to be alive or dead so presumably he escaped somehow, someway. On top of this there have to be other key members of Daath its impossible that only Yuu is important, and on top of all this if Guilty Crown: Lost Christmas is a cannon prequel then its possible that whatever organization that Present works or worked for is Daath in which case i have a feeling that a Second Season is pretty much garanteed
What im really conscerned about is when are we gonna get to watch all this in english lol