As emerging technologies increasingly blur the line between humans and machines, human–machine interaction (HMI) is poised to evolve into deeper forms of human–machine integration. This review examines conceptual frameworks and future scenarios for human–machine systems, focusing on human-centric values and agency. Drawing on foundational models of human–automation interaction and recent advances across multiple disciplines, we delineate integration paradigms from external interfaces and wearables to embedded interfaces and societal-scale intelligent environments, and survey research in each domain. We explore potential futures ranging from human–AI competition to collaboration and symbiosis, to hypothetical merging of humans with intelligent machines. We identify key considerations for steering these futures: defining beneficial outcomes for humanity, preserving human agency and rights as machines gain autonomy, ensuring inclusive benefit for those who do not adopt technological enhancements, and securing foresight capacity to guide integration in line with human values. By synthesizing research across HMI, brain–computer interfaces, Industry 5.0, AI ethics, and adaptive governance, we highlight strategies for human-centric interaction and integration frameworks that can inform technological design and policy. We decompose societal-scale integration into three stages ordered by exit cost and indicate which mapped principles are established, transferred from adjacent domains, or newly proposed. For each research community addressed, we state one implication for reporting or regulatory practice.



