Yoshinori Kitase, producer of Final Fantasy XIII and XIII-2, teased in this week's Famitsu that the next stage in the Final Fantasy XIII project will be announced at the Final Fantasy series anniversary event.
Referred to as the Lightning Saga, Kitase plans to reveal more when the anniversary event is held from August 31 until September 2, and the official Lightning Saga topic will be covered on September 1. He didn't detail the project yet, but he did say that the project has recently started production, and the project will receive an official title at the official presentation in September. Until then, unfortunately, we can only speculate on what could possible happen with the Final Fantasy XIII series. PSU will keep you informed as more information arises.