It's been almost 20 months since the last Terraria update; one that, for a long time, was destined to be the
Terraria update. Now, though, the 2D sandbox is coming out of retirement for one last
patch. Re-Logic's Andrew "Redigit" Spinks announced over Twitter that the 1.2 update would be mining through the Steam tunnels on October 1st.
The news you have all been waiting for... The update will be out on October 1st!— Andrew Spinks (@Demilogic) September 11, 2013
Given that the update has been in development since the beginning of this year, details of its features and additions are spread out over months of small teases and spoilers. It'll likely be a major revision to the game, with new items and features to be found across the majority of its existing systems. Basically: expect a little bit of everything.
Some of the features were rounded up in a teaser preview that was posted back in May:
Further details and a new trailer are expected next week.