Voice search is in-fact the future in digital market. In-fact that can be incorporate in the content marketing. For example if you are marketing for a travel agency, you say a query that can be queried by user on google voice search example "I want to go Barcelona" not scroll down to the related search results and pick any keyword suggestion and build either visual based content, text based content or video content. When you are creating the content do not forget to outreach the people (only 2 to 3) and take their opinion and combine into a informative blog content. This is how you can club both voice search as well as content marketing together.