Known problems without readily imaginable or implementable solutions include:

• Nuclear weapons: Governments in possession of nuclear weapons are unlikely to abandon them. The technology cannot be unlearned. We can only hope that the number of nuclear warheads is reduced.
• Artificial intelligence: Futurologists believe that AI will eventually put an end to work itself. How would we react to a world without work?

Safety protocols aimed at preventing accidental nuclear conflict and ethical standards in AI development will be useful, although rogue agents can still sow chaos.