Word has it that Hyrule Warriors launches for Wii U in Japan on August 14, 2014. That comes direct from Famitsu and there's of course no news on a Western date yet. However, some bits and pieces have been translated, such as the game's inclusion of "unexpected" playable characters. There's an image of Impa in the article! Maybe Impa is among them?
This is being developed by Dynasty Warriors' own Omega Force under the supervision of long-time Legend of Zelda series producer/director Eiji Aonuma. According to Famitsu, Team Ninja head Yosuke Hayashi is working on Hyrule Warriors as a producer alongside Hisashi Koinuma.
I'm strangely hopeful for someone who isn't super into either series. Something about this combination speaks to me and it's another thing to play on Wii U. Feeling good about it so far, ahead of E3. That's one sale you can count on, Tecmo Koei. Plenty more left to go.