If an agency like NSA, BND (Bundesnachrichtendienst), GCHQ, etc. were hiding million-qubit Quantum computers that don't exist yet, they could probably crack containers in very short order (minutes/hours). Otherwise it's not something to be worried about but even if a nation-state can't successfully brute force attack the container, they have other means at their disposal such as ordering you to provide the key or go to prison. For example, the UK Regulation of Investigatory Powers Act requires persons to decrypt information or supply keys to government representatives to decrypt information without a court order. Failure to disclose carries a maximum penalty of two years in jail, or five years in the cases of national security or child indecency.