Data science is a field of Big Data geared towards providing meaningful information based on large volumes of complex data. Data science, or data-driven science, combines different fields of work in statistics and computation in order to interpret data for the purpose of decision making.
Data scientists are in high demand, with forecast from IBM suggesting that the number of data scientists will reach 28 percent by 2020. In the US alone, the number of roles for all US data professionals will reach 2.7 million. Demand is clearly outstripping supply for data scientists.
Think about the demand for programmers. People asked similar questions about software developers too. Nowadays programming is not a difficult thing at all. People can find lot of resources online and it becomes extremely easy to write a mobile app or develop a website today with the help of many good tools and frameworks. Therefore, the number of software developers is increasing in a much faster speed than ever before. However, the world is still craving for software engineers - not only talented and highly experienced software engineers are in demand but also ordinary software developers because many software development jobs today don't require extremely high programming skills like they used to.
Now it's the same thing for the data scientist. More and more companies will setup such positions inside them in the future, thus the demand for data scientist will continue to increase. In the near future, the supply won't exceed the demand.
Though I believe software engineering will be automatic enough such that we'll actual need fewer software developers in some point of the future. I don't think data science can be automated in the same way. Data science is about mind work, just like designs, arts, etc. Therefore, there won't be a dramatic decrease in the demand for data scientist in the future unless we invent the true artificial intelligence.