We are working on Minecraft Beta 1.7, which I’m referring to as the “adventure update”. We’re keeping the details secret so people can get surprises. The idea with this update is to flesh out the game a bit, making it reward exploration and combat more. Assuming we like them in play testing, pistons are coming in 1.7.
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We’re starting the modding support on a small scale with 1.7. We’ll be giving the source code out to a very VERY small group of people before the release of 1.7. We’ll use those experiences to work out the final details, then we’ll get the modding api out as soon as possible after 1.7 has been released.