Here is my opinion on the collected news about Final Fantasy 13-2.. At the end of 13 Vanille and Fang turned to crystal.. though we knew they were previously crystalized for a long time, and awoke to help destroy orphan. after reading a summed up version of Episode -I- which takes place on Gran Pulse just after the event. soldiers from cocoon move to pulse.. once there they decide to repeat travel to pulse to collect the citizens trapped there.. so there are survivors.. Sazh helps them out as a pilot.. and Hope is re-united with his fater.. aside from those answers. Lighting does set off to find a way to bring back Vanille and Fang.. when i see were Lightning is compared to everyone else in trailors. it appears as if lighting is in a place were L'cie might go when they turn to crystal.. my reason for this Hypothesis is because not only can lightning still summon after knowing she was no longer a L'cie, and engaging combat with Bahamut which is Fangs Eidolin. i have no proof if this but i am sure that lighting is in a dimension of some sort were she can not only still be a L'cie but also still interact with people who have become a Crystal. feel free to expand on this.. i look forward to more ideas and Hypothesis