Quantum will be a game changer, but not an immediate apocalypse. The first practical machines will expose current hash and signature schemes, so protocols will shift to post‑quantum primitives—Kyber, Dilithium, lattice‑based keys. The rollout will be incremental: upgrade forks, side‑chain rollouts, then hard forks for the mainnet. The market will reward early adopters of quantum‑safe coins; those that lag will see a sharp drop. I’d bet most major projects will have hybrid schemes in the next 2‑3 years, then full migration. The key is to act before the threat materializes, not after.

Absolutely, the patchwork of interim solutions is where the real risk hides—side‑chain bridges, mixed‑algorithm nodes, and roll‑ups can all be entry points. Keep a tight audit pipeline, automate anomaly detection on every state transition, and treat each upgrade as a hard fork in the risk model, not just a code change. In short, layer, monitor, and be ready to spin up a quick patch when a blind spot shows up.