Upcoming features

Terraria 1.3.1
The Terraria 1.3.1 update will be focused around improvements and additions to the wiring system of Terraria. Players are encouraged to send in their ideas here. Spoilers: Yoraiz0r has confirmed logic gates (AND, NAND, OR, NOR, XOR, and NXOR) and Yellow Wire. Links to Yoraiz0r's gifs: AND gate Yellow Wire

Terraria Series
Following the release of the Terraria 1.3 update, very few concrete plans for future additions or updates have been mentioned by the developers. Lead developer Redigit has moved on to working on Terraria: Otherworld, though developers Yoraiz0r and Skiphs plan to continue updating Terraria into the future.

Redigit has also stated that he plans to later release Terraria 2, a seperate game from Terraria: Otherworld, although little information is known about the nature or content of this sequel.