There's been no official explanation for the date being pushed back but Pandemic teams have been rather busy with Mercenaries 2 and Lord of the Rings: Conquest.
Saboteur is a freedom-fighting action-adventure that pits the player against Nazi occupation. Other than getting to stick a giant to fingers up to the Third Reich, the game's world itself would transform from a dull, bleakish black and white to full rich colour as you progress through.
This feature however hasn't been confirmed as staying in the videogame; it was inspired from Steven Spielberg's 1993 Schindler's List where everything was shot in black and white.
Source: VideoGamer.com