There will be no public announcement that it's outright cancelled. Basically, I think FF Versus XIII may never release and SQEX are scared to publicly announce this. They plan to string people along for as long as possible like they did with The Last Remnant PS3. They hope people will just lose interest in the game and forget about it over time.
I think even Japanese magazines know that it's cancelled as none of them asked Tetsuya Nomura about it during interviews in March 2013 when KH 1.5 HD was released in Japan. These same Japanese magazines have stopped asking about the status of the The Last Remnant on PS3.
Well, E3 will show us the truth. If the game gets no playable demo or even a trailer, it's safe to start believing this game is canned and SQEX are just stringing us along with the statements like, "Please look forward to it." They're going to keep spouting that BS until we lose interest and stop asking about the game.