The cybersecurity world has experienced a generational shift from system-based monitoring and border protection to wholly autonomous, AI-powered systems. The current paper follows the development of cybersecurity architectures across five generations and concludes with the 5.0 paradigm, characterized by agentic AI, Zero Trust architecture (ZTA), and self-directed incident response. Using the latest empirical sources, the paper will explore how machine learning, adversarial AI modeling, and autonomous response mechanisms are transforming organizational security postures in an age of increasingly sophisticated threats. It has been established that AI-based systems significantly reduce detection latency and breach costs, but at the same time pose governance and adversarial risks that will require preemptive policy-technical efforts (Kshetri, 2025; Adeyemi, 2023).