Is Data Science just a trend or is a long term concept?
The one thing that you can say for sure is: Nobody can say this for sure. And it might indeed be opinion-based to some extent. The introduction of terms like "Big Data" that some people consider as "hypes" or "buzzwords" don't make it easier to flesh out an appropriate answer here. But I'll try. 

In general, interdisciplinary fields often seem to have the problem of not being taken serious by either of the fields they are spanning. However, the more research is invested into a particular field, the greater is the urge to split this field into several sub-topics. And these sub-topics sonner of later have to be re-combined in new ways, in order to prevent an overspecialization, and to increase and broaden the applicability of techniques that are developed by the (over?)specialized experts in the different fields. 

And I consider "Data Science" as such an approach to combine the expertise and findings from different fields. You described it as


  ...a mix of computer science and statistics techniques


And indeed, several questions here aim at the differentiation between data science and statistics. But a pure statistician will most likely not be able to set up a Hadoop cluster and show the results of his analysis in an interactive HTML5 dashboard. And someone who can implement a nice HTML5 dashboard might not be so familiar with the mathematical background of a Chi-Squared-Test. 

It is reasonable to assume that giving students enough knowledge to apply the most important techniques from the different fields that are covered by data science will lead to new applications of these techniques, and be beneficial - also for the "purists" in these fields. The combination of these techniques is not straightforward in many cases, and can justify an own branch of research. 

You also asked whether in 10 years, data science will be considered as "just a topic inside computer science". Again: Nobody can say for sure. But I wonder at which point people stopped asking the question whether "Computer Science" will one day only be considered only as a mix of (or a subject of) Electrical Engineering and Mathematics...