Maybe Sony shouldn't have sold their stock. By doing so, Square Enix is not really obligated to show anything at any Sony event.
That said, Square Enix will most likely do their own thing at TGS. Yes, they didn't show Final Fantasy XV, but they didn't show Final Fantasy Type-0 HD either and that comes out in less then a year. A bit strange don't you think?
Many are acting like TGS is over already when it hasn't even started yet. Not everything has to be revealed at these big press conferences just because they make perfect sense. Time to put that way of thinking aside.
So cheer up! All is not lost yet.