It is vain to think or imagine things that is or are not possible, in a scale of zero to ten, the chances that all Bitcoin will ever be lost will always remain at zero.

And to answer you more appropriately, what will happen if all is lost is that, I will become the only bitcoin hodler and will sell one satoshi for $100,000 each, this is because if every one else is losing their bitcoin, I will never lose mine  .

On a more serious note, like I said before, there will always be 0.00000000 percent chances of all Bitcoin ever being lost, so, it is vain to imagine what would happen if this happens.