Artificial intelligence (AI) capabilities in natural language processing are rapidly advancing and transforming communication practices across diverse contexts. This review provides a comprehensive analysis of AI's emerging roles in mediating and participating in direct communication to highlight key opportunities and research priorities around responsible innovation. The study surveys the extensive literature on major applications of AI, including virtual assistants, chatbots, smart replies, sentiment analysis tools, and automatic translation technologies. It also closely examines their current and potential usage and benefits across interpersonal, organizational, and societal communication. The analysis reveals these AI technologies promise enhanced efficiency, personalization, accessibility, and new modalities of expression in communication. The study found that if judiciously and ethically applied, they could incrementally improve communication speed, quality, relationships, and even therapists' capabilities over time. However, more rigorous research is still recommended to investigate longitudinal impacts on human well-being, increase accessibility for vulnerable demographic groups, advance multimodality AI systems, and develop tailored guidelines and user-centered studies to ensure ethical, socially responsible progress. Overall, this review synthesizes the current state of the science and pressing research needs in this rapidly emerging field.