That doesn't mean the game's getting cancelled, however. The announcement emphatically states that Age of Empires Online will continue to operate as is, will have future community events, and it is not "dying."
The move from development to support was explained as follows: "Creating top-tier content, as we have been for the last year and a half, is very expensive -- too expensive to maintain for long, as it turns out. We can no longer afford to keep creating it. Age of Empires Online already has a very large amount of high-quality, hand-crafted entertainment, and adding more is no longer cost-effective."