Delay a month, then you've got a different problem of releasing too close to the DEATH BRACKET of Call of Duty and Halo!
One may argue different genres, but when you're talking about casual gamers, they are going to be picking up whatever draws their attention THE MOST, and for many, NO GAME draws as hard as COD and Halo ... and you have to figure with the two of those games releasing the same month, not a lot of casuals will be likely to want to drop $$$ on a "third" game (which DOA5 would be on their to-buy lists) less than a month prior/following those two.
Then you have to question which game(s) are most likely to be bought come Holiday season (for those who are dependent on the Holidays for getting new games).