The patch is available now. This is all from memory, so I could be wrong, but the patch adds:
- A new RV/campground area where scanned amiibo characters (and other characters not scanned) will appear. You have to first get a magic lamp to make Wisp appear; Wisp is basically your amiibo interface.
- These characters can be asked to stay in your village.
- Compatible amiibo are mostly (entirely?) Zelda, Splatoon, and Animal Crossing.
- New furniture/clothing have been added based on HHD and Nintendo crossover content, unlocked via HHD save data, amiibo (character shows up in campground and then can purchase the items from the villagers who show up), and other means that don't require amiibo (not true for everything, though).
- Of the items that anyone can get, Wii Us and 3DSs were added as furniture items (I think they're accessible through amiibo characters or the roulette, if that's a thing?). If you have a Wii U, you can play the Desert Island Escape minigame (from amiibo Festival). With a 3DS, you can play Animal Crossing Puzzle League. amiibo can assist you in these.
- The decorating interface from HHD (that uses the touch screen) has been added.
- A photo mode has been added for taking pictures of your villagers.
- New optional Daily and Weekly missions have been added. If you complete these, you earn MEOW coupons. MEOW coupons can be used to order items and redeemed for money. These coupons are also what's used to purchase from RV villagers, I believe.
- You can now have a secret storage area in your house that allows you to basically save extra stuff. This is not an extra room, but more like an extra menu, so it won't be visible to anyone visiting.
- If you want to start over with this new update, you can have your old village evaluated and Tom Nook can give you (potentially lots of) money to begin your new village.
- New Sanrio (Hello Kitty) amiibo cards are releasing (this hasn't been announced for NA yet).
- Lots of other little tweaks and additions that people are discovering.
This list summary from Nintendo UK might help:
http://www.nintendo.co.uk/News/2016...-Animal-Crossing-New-Leaf-update-1151452.html