Toriyama: "Yes, certain enemies will reappear. One of these will be Caius, because at the end of XIII-2 there is an uncertainty that hovers around his destiny and whether he survives or not. This mystery will be solved in Lightning Returns."
"Despite this, they made no mention of whether we would actually see Caius again or if he is simply mentioned during the course of the story."
Sure, because there was any uncertainty left over after Caius forced Noel to kill him and to break the universe which then prompted his immediate revival with a diabolical Mwhahaha! to boot because the clown was an immortal Marty Stu.
Unless he's referring to the fact that they're retconning the ending of FFXIII-2, because it really really needed it.
Hell they've already brought Serah-chan back from the grave (twice) even if she's not quite the same character anymore, there's no way in hell they're not going to use the assets they made for Caius again.