An additional explanation found here.
As a fan of Terraria, I look forward to the day when he designs a new game with what he has already learned with his experiences with Terraria. Much like many other game developers I follow, they all seem to have ideas and plans that they wish to implement on a game, but ones that can't be applied to their current games, so hopefully moving on to a new project will open new doors to greater games.
In the meantime, however, Redigit also posts a link to a game that looks and plays somewhat similar to Terraria, called Starbound, by Chucklefish. Although this game also has randomly generated "worlds", there is more to it than just exploring the worlds. Despite being a sandbox game in nature, this game also has a story.
Planned release date appears to be Summer, 2012 so far, but we'll see how it goes.
Back to Terraria for now, despite Redigit discontinuing official updates for Terraria, there does appear to be some other fans who are making mods for Terraria to add new, unofficial content to add more things in Terraria. One of which that I'm aware of is the Reborn Mod. Here's the trailer.
Aside from that, there have been some players who push themselves to do some challenges that ... may be pretty crazy, such as this one in this video by Yrimir.
Absolutely crazy. >_>; Yrimir has been posting lots of challenge videos, including Hardcore Speedruns to getting Excalibur and other fun videos. If you're into Terraria, I would recommend subscribing to his YouTube channel.
Well, I've been meaning to post some screenshots of my own worlds and such, but I really haven't been playing Terraria as much lately, due to other interests at the moment, but I would like to get back to doing some neat projects with building interesting things on Terraria again. I doubt I could make anything better than what many other people have already made though, like those that get featured on the official website.