Alright here a couple spoliers for the updates :D

All taken from here

(Not everything will all be in ONE update there will be MANY)

Christmas Updates

  • Customizable Christmas trees with animated lights.
  • A pet elf (touch screen's)
  • Zombies in elf and santa costumes
  • Slimes in gift and ribbon costumes
  • Festive Grappling Hook
  • Festive Wings
  • Eggnog, an 80 HP health potion.
  • Candy Cane hearts (much like the Candy Apple hearts of Halloween)
  • Red Potion that gives you every buff for an hour and heart sprites
  • A Candy Cane sword
  • Ruldolph, a flying Reindeer Mount summoned by the Reindeer Bells. The antlers will also be varied.
  • Santank, the Christmas boss who will drop said Bells.
  • An extra Frost Legion member

Lunar Update

  • The Lunar Boss.
  • The SDMG
  • The SteamPunk Wings
  • Lots of bug fixes.
  • Professional language translation.

Upcoming Features

  • A buff to the Golem
  • A Portal Gun
  • Alternate Underground Theme music.
  • New harder world types:
    • Alien planets
    • Alternate dimensions
    • Evil worlds
  • Enemy factions that will move into your world, and build their own city.
  • More events
    • Volcanoes
    • Earthquake
    • Lunar Event
    • More/improved invasions
  • Official Modding Support
  • Weather
    • Floods
  • Farming and stamina system that gives a bonus to player stats.
  • Implementation of Steam features
  • NPCs which can give quests to provide more content.
  • New items
    • Portcullis
    • Flag
    • Fishing Pole
  • New furniture:[tweet 1]
    • Weather Vane
    • Telescope
    • a wall mounted fish
    • Window with Curtains
    • Bell
    • Cuckoo Clock
    • Mirror
    • Wardrobe