A million possibilities - hell, there’s an entire section in book stores dedicated to it.
Could be dystopian, could be utopian…
Overpopulation would correct itself eventually.
I think the most likely outcome is a technological singularity (nothing new or creative here - yeah Skynet). But I think that’s most logical. We will eventually create an artificial intelligence that considers us obsolete and deems us more of a risk than a benefit unless we can figure out a way to remain a benefit.
That being said, I think technology is the only thing that will defend us against the most realistic threats to our existence - an alien threat (which as some point seems inevitable) or global climate change (not man made, just climate change in general). I don’t know that these are 1,000 years or less away, but they seem like they will become a reality at some point.