You can access the roadmap from the main menu in the game, but if you don't have access to the game right now, see below.
If the photo does not work for you, read below for a transcript of what it says.
Appreciation update - May 2019 (already released)
- New game modes.
- Weather effects.
- Quality of Life Changes.
- Improved Options Menu.
Combat Update - Summer 2019- New Biome.
- Hard Mode.
- New Bosses and enemies.
- Improved Combat difficulty.
Mod Support Update - Fall 2019- Custom Biomes.
- Custom Items.
- Custom Structures.
- And much more!
Multiplayer Update - Winter 2019/2020- Play with your friends.
- New Lands.
- New Items.