Relax.. It's just been pushed back 2 weeks to give more time to polish the game, according to Ubisoft. The new Release Date is Nov 11 2014, same day as AC Rogue's Release Date.
Standard excuse as always. Polish the game..
It could also be a marketing decision, or something to do with the plot. It's reported that AC Rogue will have ties with AC Unity so that might have affected the decision to push it back to the same day as AC Rogue.
I wonder if this will affect Far Cry 4's Release Date in any way..
Would have preferred to get AC Unity slightly earlier so I can start on it before moving on to AC Rogue but oh well..