Nowadays, it will be difficult to find a full-time job like this at design agencies. You can aim to gradually take on this role after you work for a company for a while or do it part-time similar to Google’s model. Sometimes I come across freelance projects that are far future oriented, and technology companies are often looking for implementations to showcase it, a nice example being Crealev. Philips Design has a Design Probes department where designers explore the far-future so it can trickle down into products they are currently working on - I know they are open to new people if they have extraordinary ideas and approaches. You can also look into working for a design research department such as DQI at Eindhoven University of Technology or at the RCA with Bill Gaver.