Agni's Philosophy is pretty much what that remade FF VII intro was: a display of raw graphic and engine power for our eyes to feast upon and get even more interested in current and future Squeenix projects. And man, does it work. Now, since both are tech demos, they're not happening as games. That's why I believe Agni's Philosophy is just a very nicely done short.
That does not mean we won't be getting any FFXV news next year. In fact, I have my suspicions that they've already begun working on XV, since it won't take less than four years to see the light of day anyway. When we'll hear about it is another matter altogether. Guess when they have something for show, on the TGS or on a event of their own.
Also, Versus will be the first title Nomura will be directing, so I'm pretty sure they have another name up their sleeve for XV.