Command blocks were added to the game, but were only accessible through third-party tools; then they removed the texture for them, making them essentially an X-ray block; then they corrupted them, which completely crashed any world with one; I haven't checked to see what the most recent version does with them. They never worked during any of this.
Let the trend of what has happened to them be my answer,
The Meaning of Life, the Universe, and Everything.
They're not really stopping the updates for the game they are just still thinking of ideas for new block, mobs and other things for the next big update. The most recent updates was just to change some mechanics for a few things and a few bug fixes. Big updates take awhile. Even if there is a big update for pc it'll still be awhile for xbox 360 to get that update cause it doesn't get released for all platforms all at once. They have to reconfigure a few things for them to be compatible for each console which I guess is a bit of a lengthy process for each flatform