Terraria has been rated by the German USK board, indicating an imminent release announcement in the future. The ratings board rated both a Wii U and 3DS version of the title, and revealed that both titles are in development by 505 Games.
This is not the first time that Terraria has been spotted in relation to the Wii U and 3DS. Earlier this year, listings popped up on Gamefly for both versions of Terraria. There is still no official confirmation from 505 Games on the existence of these ports; however, the German USK board is very reliable due to the fact that all games cost a fee to be evaluated and cannot appear without the payment of the publisher.
Source: Nintendo Enthusiast