I believe it'll have a "big length trailer with gameplay footage" that will reveal the title, some early story "teasers", combat/menu basics, and whatever the gamepad usage will be. It's also quite likely that it could have a playable demo on the show floor, but it depends on whether Nintendo goes with the idea of "focusing on titles releasing this fiscal year" (ie. through March 2015, so NOT Zelda in my opinion) or if they (wisely/correctly) try to build some hype by offering trailers and demos for ANY/ALL games that are far enough along to do so, Zelda especially included.
Upcoming Games To Get
Definite: Kirby Star Allies (Switch), Mario Tennis Aces (Switch), Fire Emblem (Switch), Yoshi (Switch), Pokemon (Switch), Kingdom Hearts 3 (PS4), Monster Hunter World (PS4)
Considering: Fe (Switch), Donkey Kong Country Tropical Freeze (Switch), The World Ends With You (Switch), Ys VIII (Switch), Street Fighter V: Arcade Edition (PS4), Kingdom Hearts 2.8 Remix (PS4), The Last Guardian (PS4), Shadow of the Colossus HD (PS4), Anthem (PS4), Shenmue 3 (PS4), WiLD (PS4)
