Seeing how close the game is to completion, that they have a demo scheduled, and the amazing amount of money they were throwing around at Comic Con in Ghostbusters stuff and just promoting the game. I really doubt they cancelled it, seeing how much money they would lose.
Not having a release date really could mean anything, with all the amount of games coming out in the October/November Time Frame, Activision could be trying to position the game for a week in which it would get maximum exposure.