Notch has tweeted to say that Minecraft's 1.4 update will be landing very soon. "The plan is to release 1.4 this week." he says, "stats and achievements require more work than expected." Notch also updated his blog to say that the update will add wolves, and the ability to change your spawn point. Notch recently put out a video of the new wolves . They're adorable.
As for plans beyond the 1.4 update, Notch says the team will be working on community creation tools. "Once that update is out, we'll spend some time figuring out exactly what to do with the modding, which should result in a nice modding API."