The creator of Terraria, Andrew "Redigit" Spinks, has revealed to Rock, Paper, Shotgun that the mystery project he quit Terraria to work on is in fact Terraria 2. Spinks stepped away to work on this mystery project but eventually released a substantial update to the first game before returning to work on the sequel. He has his sights set high for his next game, hoping to expand on the gameplay and offer gamers even more customization options. "In Terraria 2, I really want to have infinite worlds so you’re not just stuck to one world. You can travel anywhere. I want more biome diversity in that, too. There’s a lot of stuff [I want to add and change]." He also added that another update may come to Terraria, perhaps Halloween themed, and pointed out that nothing is set in stone for now.
Source: Rock, Paper, Shotgun