Nintendo Direct press briefing today.
The game will be available in Europe and North America in March 2013, and features online multiplayer. Fils-Aime highlighted cross-platform multiplayer as a feature for the game, allowing players to progress their characters across Wii U and 3DS versions.
Nintendo's Wii U system was dated and priced at the press briefing today as well.
Update: Capcom sent us a press release with more features for Monster Hunter 3 Ultimate, including over 200 quests, touch-screen inventory and map functionality, and a "guild card" that can be swapped with other players using the 3DS' Street Pass feature.
Players will also be able to transfer their save data between both systems. The 3DS version supports local four-player multiplayer, with no mention of online play for the portable version.
Update #2: We've added an announcement video above from Monster Hunter 3 Ultimate producer Ryozo Tsujimoto.