I agree with everything Pokemanz has said earlier about what to expect in the Wii U installment. Where the Wii version suffered was the lack of the second screen. Luckily for the Wii U version, it won't be at such a handicap. I feel like the GamePad is perfect for this game.
Here is what I want to see:
*Villagers are more unique: They have new traits, interests, desires, likes and dislikes.
*More in-depth PWP/Town Hall functions: Arrange town hall meetings with villagers to help decide future PWP and plan your own events! Hear what villagers have to say about how the town can improve and what should be done more (ie set ordiances, plant more trees, suggest villagers do voluteer work, etc.)
*Friendship meter: The more you communicate with your villagers the more their meter increases and decreases their likelihood to move out of refuse to do volunteer work.
*Take to the air: In past games, you arrived to your village by train, taxi, bus and trolley. Now you will arrive in a hot air balloon! You can also travel to other villages this way!
*Vegetation: Before, you only planted fruit trees, but now you can put your gardening skills to the test with new vegetables you can harvest and sell. Carrots, Lettuce, Cucumber, Potatoes, Squash, Tomato, and more!
Volunteer Work: At your town hall meetings, you can ask villagers to do various tasks, with a proper incentive attached if need be. Tasks include tending to vegetation and fruit trees, pulling weeds, doing errands for other villagers, form a welcoming committee, form a singing group and carrol around town, be an instructor for different events like exercise day, dig up and collect fossils, etc. Basically make your villagers feel more involved.
Villagers actually do more on their own: Fish, catch bugs, swim, jog, group conversations, enter/exit buildings, etc. Plus you can enable a round the clock scrolled that tells you what is going on in town, what villagers are doing, what villager is looking for you etc. Almost like a notification system.
Big world: Think Zelda Wii U sized villages but with the usual animal crossing patterns. Sprawing fields, tons of trees, nearly twice as many villagers as the GC version, and a big beach!
Islands: You can own idividual islands and build your own house or permit villagers and shops to move there! Tortimer Island returns as well as the debut of some of his offspring.
360 degrees: No more top down view. Your village will be fully rotatable and viewable at all angles!
Import: By connectIng with the 3DS game, you can import your human villagers, animal villagers, furniture, clothes, designs and almost anything else.
If none of the above happens, then they should at least bring Champ back.
I think the mayoral aspect was such a genius concept before that I can see it be more expansive in the Wii U. They are really promoting Isabelle as a prominent part of Animal Crossing means she's here to stay. Its also odd that the AC DLC Pack for Mario Kart 8 is being released in May. It seems rather late, unless that was done on purpose to tie in with the Wii U game announcement.
Please forgive me for My writing. Im typing this on a smart phone so it's more difficult.
EDIT: I made similar suggestions many moons ago so now. I feel like a broken record. :/