You think that, without using uploads or AI, humanity has less than a 50% chance of surviving the next hundred years? That seems very surprising to me.

Viral threats are a danger, yes, but while they may cause massive depopulation, even kill off a significant fraction of Earth's population (especially if genetically engineered viruses are used as a terrorist weapon), they seem unlikely to be able to kill off everyone - especially if people on small islands start shooting down any approaching planes to prevent contamination. Nanotechnological threats may be more all-inclusive, but while that might destroy an entire continent, it would seem unlikely that nanotechnology that can cross an ocean before countermeasures can be developed could be created accidentally

And within thirty years, there's even a chance of a small colony on Mars - if they can get to the point where they're growing their own food, rather than having it shipped from Earth, and where they have enough people to sustain their population, then even something that renders Earth uninhabitable would not wipe out all of humanity; and the Sun appears stable enough to keep going for a good few million years still.

So... am I misunderstanding you, or do you see some threat to humanity that I fail to notice?