According to Amazon, it looks like we can expect Splinter Cell: Blacklist in April 2013.
The bonus DLC includes the ‘Upper Echelon Suit’ consisting of five armour pieces “with a unique visual and damage protection bonus”, Special Goggles and an unspecified bonus mission. The A2 poster is a global map of the conflict zone Fisher will be visiting in Blacklist.
Splinter Cell: Blacklist is available to pre-order on Amazon, with the Upper Echelon edition offered as a free upgrade incentive. Splinter Cell: Blacklist will be launching on April 1st, 2013 according to the listing, although Ubisoft has yet to confirm an official launch date.
My guess is that the release date will be set for April 2nd which is the usual Tues release day we see for games.