Mafia II and Red Dead Redemption have both been delayed "to allow additional development time for the titles and to maximize their full potential in terms of the quality of the player experience and market performance." In other words, the development teams needed a bit more time.
The two titles are now planned for the first half of fiscal 2010, which spans November 2009 to April 2010. This means either of these games can still make the all-important holiday shopping season. However, even without Mafia and Red Dead Redemption, Take-Two still has a relatively strong lineup with BioShock 2, The Ballad of Gay Tony, and Borderlands.