According to this week's Famitsu, "Hyrule Warriors" will be released in Japan on August 14. It as also been confirmed that Team Ninja has been working on the title. Expect some update from Nintendo about this game's western début soonish, maybe even before e3.
*OMAKE* From Nintendo Life:
In terms of the teams working on the project, Warriors franchise veterans Omega Force are primary developers, though Hisashi Koinuma and Yosuke Hayasahi of Team Ninja are named as producers on the project, with Nintendo's Zelda series producer Eiji Aonuma in a supervisory role.