Design visualization is a career, but computer graphics in general actually has really broad ranges of opportunities. Most of them require a good deal of experience with specific tools.
Product rendering is a niche, but just using the rendering software isn’t enough, especially since most kids graduating design school will have a fairly decent breadth of rendering work if they are interested in the field. You need to understand photography and lighting (what makes a good photo is equally applicable to a good rendering), compositing (layering different images together to create the desired result, like a car on a mountain road), shader design (how to make materials look true to their real world counterparts), and a variety of 3D modeling techniques (NURBS, polygons, SubDs, each has pros and cons). Many times pure CAD data is not good enough for high end renderings and the person in charge of rendering will have to recreate objects to make them more true to form or natural looking.
There are other niche markets like architectural visualization (rendering spaces and buildings), visualization for VR will have growing opportunities as well I think.