LOL. That is a useless unnecessary question. This is never going to happen. Even if it happens, You and I won't be there to see it.
The question is just laughable. Like you, @LearnBitcoin, said as an assumption, even if it is possible, I don't see such happening. OP forgot that there are bitcoins in the possession of different people, and there is no way that everyone can just lose all the bitcoins in their possession. This discussion is just a fallacy; there is no way to even think about how such a thing can happen.
Some people have Bitcoin in their wallet and no one is aware of it; some will die, and their Bitcoin will be trapped in their wallet for ever because no one will have access to it unless they themselves, but that's not going to happen the same for Bitcoiners. Some people will still transfer their Bitcoin to their loved ones, and they will continue to be in possession of their Bitcoin.
According to the OP's assumptions, don't even think about it because it has a 0.5% chance of happening. Why? Because the only way such a thing will be possible is if everyone on earth who has Bitcoin in their possession dies and there is no way to recover their Bitcoin. That's only when such a thing can be possible, but the truth is that everyone will not die at once without passing their Bitcoin to their loved ones.