The emergence of quantum computing represents one of the most significant paradigm shifts in the history of computation, with profound implications for offensive security and cyber warfare. This comprehensive research paper presents a systematic analysis of quantum-enabled offensive capabilities, novel attack vectors targeting quantum systems themselves, and the evolving threat landscape at the intersection of quantum computing and artificial intelligence. We introduce the Q-THREAT Framework, a novel temporal risk assessment model that quantifies the "Harvest Now, Decrypt Later" threat across different data confidentiality lifetimes and sectoral exposures. This research synthesizes and categorizes recently documented attack vectors including quantum Rowhammer exploits, timing-based side-channel vulnerabilities in cloud quantum services, and multi-tenant quantum system intrusions. Recent research demonstrates that current quantum cloud platforms from major providers including IBM, Rigetti, and others exhibit significant security vulnerabilities that could be exploited by adversaries to compromise computational integrity, extract sensitive circuit information, and disrupt quantum computations. Furthermore, we analyze the convergence of quantum computing and artificial intelligence as a force multiplier for offensive cyber operations. We present evidence that quantum machine learning algorithms can demonstrate competitive or superior performance in certain cybersecurity applications compared to classical approaches in controlled experimental settings, with recent studies reporting high accuracies in tasks such as malware detection and intrusion detection on benchmark datasets. Our analysis of nation-state quantum programs reveals an accelerating global quantum arms race with significant implications for national security. Based on our findings, we propose a comprehensive defensive framework incorporating post-quantum cryptographic standards, crypto-agility principles, and quantum-safe architectural patterns. This research contributes to the nascent field of quantum cybersecurity by establishing foundational threat models, identifying critical research gaps, and providing actionable recommendations for organizations preparing for the quantum era.