Most likely changing climate will break down our globalized world and lead to seclusion in a harsh environment. Over several hundred years and the fact that genetic engineering technology might speed things up, we could see such conflict and environmental factors either wipe out humanity or some sort of assimilation and interbreeding wipes it out that way.
We have a good chance of being pushed into ending up as Neanderthals by our own hands, so expect some later warfare and bloodshed. The last human will live afraid and destitute, but won’t be the last person.
Basically technology would still advance even as society fragmented and as a result, as larger communities became isolated, they would change themselves and their environments to continue their way of life. The smaller communities in the less inhabitable areas would be expelled and eventually exterminated to reclaim more resources for the altered resurgent communities. Basically, you see the last human living and dying the way island natives once did.
Not only does it not contradict what I said, but it completes my expectation in an analogy that works out somewhat well (“Island natives” are still here)
Genetically-engineered beings who don’t resemble humans are the scenario that not only is the most hellish in the worst of what could happen, but of the high likelihood of it happening.
