Will it cause damage should it hit a populated area? It certainly could. The stage is 18 tonnes in weight and a certain amount will land either on land or sea.
In fact, this is the largest item to make an unscheduled re-entry into the atmosphere in many years, and yes, you read that right, this is not planned.
The Chinese space agency has made a rather embarrassing blunder and should anything bad happen, consequences will have to be dealt with.
Satellites and rocket stages are normally deorbited in a controlled manner and the location they are aimed for is known as the satellite graveyard which is located in the Pacific ocean between Australia and New Zealand.