Oh yeah! Notifications! Something that simple would be a godsend for that game.This, exactly. Can you imagine how awesome it would be if it fully integrated some kind of asynchronous online multiplayer? Add friends, and then pop into their town even when they're away (limit destruction possibilities, but let me chat with their neighbors, leave notes, etc). Not only that but push notifications for the insane amount of special events, like fishing tourneys or even your favorite neighbor's birthday. Or better yet, when you set a time for a neighbor to come over which I would ALWAYS forget on GameCube/DS versions.
Honestly, there are too many sweet ideas for this franchise to work beautifully on iOS for Nintendo to leave it all on the table for some disappointing remix of Happy Home Designer. I see a lot of complaining about IAPs, but I'm gonna compare it to The Simpsons: Tapped Out. That game has TONS of buildings, characters, quests, etc, that are blocked behind IAPs, but it doesn't hinder the main game in any way. In three years, I've spent no money in that game, and I think my Springfield is pretty awesome.
There's a way Nintendo could fish for those players who will spend money, but leave everyone else with an enjoyable experience, and the Animal Crossing series has far and away enough random crap to lock some behind a paywall and leave the rest for the normal game.
I feel like Nintendo would put something in that automatically raises bells or something, and you have to spend money to get that upgraded or else it would take atrociously long to get it upgraded otherwise. Something like that. Also Nintendo would likely offer every collectable in the game for a small price if you don't feel like waiting around for it to show up in Nook's store. Also house upgrades, store upgrades, anything that can be obtained with bells I can see them tempting players to just buy it now with real money rather than work for the bells.
I don't see Nintendo putting up a full-fledged animal crossing game for free with IAPs. It would likely be $9.99 at least and STILL have IAPs, which would make people mad, but anyway. That's the world we live in with mobile games.