Square Enix will reveal a new Final Fantasy XIII title on September 1, but this new game has only recently begun production.
Producer Yoshinori Kitase said the new Final Fantasy XIII game has only "just entered production," with the September 1 event revealing the name. This more than likely means the new game will be Final Fantasy XIII-3 after all and not Versus XIII, unless you count 2006 as recent for the latter. There still could be some news on Versus XIII, even something as small as an announcement date, but such is life.
When Square Enix announced it would be holding a Final Fantasy XIII event on September 1, some felt it could be either to announce Final Fantasy XIII-3 or provide some major news on Final Fantasy Versus XIII. Versus XIII had been rumored to be canceled only to have Square Enix's president Yoichi Wada debunk that rumor. This gave new hope that it would be Versus XIII shown at the event, but now that does not appear to be the case.
Whatever the new project is should be interesting, and we have just about a month to go to find out. The Final Fantasy 25th Anniversary celebration kicks off on August 31 and runs to September 2.