As Qt is used for small, medium and large sized application/service development, it is very likely that NoSQL trend will not skip Qt developers. Although most NoSQL projects have background of web app development and dynamic languages, some of the current NoSQL libraries have been written in C or C++, so integration would be possible.
Example case: design social networking system with capability of ten billion people who are interconnected in various ways (various types of links between people). People links may contain properties (property names not fixed in schema), People have properties that are not fixed in the schema.