What does the plateau people speak?

The term "Plateau People" is not a recognized cultural or ethnic group. It's likely a broad term that could refer to a variety of people who live on a plateau region.

To understand which languages are spoken, you need to specify:

* Which plateau are you referring to? There are many plateaus around the world, each with its own distinct population and languages. For example, the Tibetan Plateau, the Ethiopian Highlands, the Deccan Plateau in India, etc.

* What time period are you interested in? Languages can change over time, and the languages spoken in a region today might differ from those spoken centuries ago.

Once you provide more information, I can help you identify the languages spoken by the people living in that specific plateau.