The "Harvest Now, Decrypt Later" (HNDL) quantum threat is a ticking time bomb for long-lifecycle Software-Defined Vehicles (SDVs), especially with upcoming regulations like the EU Cyber Resilience Act demanding future-proof security. However, hastily replacing classical cryptography with newly standardized Post-Quantum Cryptography (PQC) in resource-constrained ECUs introduces unacceptable safety risks, as these novel algorithms lack decades of real-world vetting. This session bridges the gap between theoretical quantum safety and harsh automotive realities. We present a practical, ISO/SAE 21434-aligned migration blueprint for establishing a sustained Hybrid PQC architecture. Attendees will learn how to implement true defense-in-depth across the vehicle edge, layering the proven reliability of classical ECC with the quantum resistance of NIST's ML-KEM and ML-DSA, while effectively managing critical bottlenecks like ECU memory constraints and in-vehicle network PKI bloat.