According to IGN.com, release date is Q1 2010.
http://pc.ign.com/objects/026/026623.html
And according to Ubisoft tradition, each game in the SH installment hit the shelves in March. So, I'd guess it's set for release in March 2010.
More from IGN:
General Features - Walk through highly detailed submarines in the new first-person view and access every part of your U-boat
- Interact with your crew, watch them perform their daily jobs and experience the tension and fear inside the U-boat through the new advanced order system
- Choose your own strategy and select your targets with a new objective-driven, dynamic campaign
- Open new locations, upgrades and resupply possibilities, while the Allied ships adjust dynamically to your approach. Your actions will directly impact the evolution of the campaign
- Prowl the waters with user interface. Every beginner can successfully command a sub while remaining free of confusion. In expert mode, experienced players will be provided all the necessary information and controls to command the sub completely on their own
- Operate authentic, highly detailed U-boats and fight against surface ships.
Now, this looks like some really interesting feature:
Your actions will directly impact the evolution of the campaign
Still no word about wolfpacks