Minecraft's creator, Markus Persson, has taken to his blog to talk briefly about the next wave of changes we'll be seeing in Minecraft - including pistons.
Yes, the next update (1.7) will include pistons and a couple of bug fixes. Persson notes that they hope to release the update soon. The following update will be the "adventure" update, but there's no ETA for when that will release.
Further to this, Persson states that they hope to have the full version of Minecraft available shortly after the week of 11/11/11 - no competing with Skyrim.