Craziest thing I can think of is a sort of biotechnological singularity.
I think it's quite possible within the next 50 years we will have the capability to accurately predict biological outcome in complex organisms from genetic sequence and have sophisticated enough tools for genetic engineering to make whatever biological outcome we want a reality. When this happens pretty much anything that can be done within the most fundamental constraints of biology will be cheaply and widely accessible. In a way it will be a significant step towards humanity merging with technology because our computational capabilities will more directly impact our material world, including our own biology.
It will ultimately produce a lot of abundance, but there will be massive changes to culture and economics that might be hard to deal with as it's happening.
- Lifespan will be significantly increased, potentially creating a lot of population growth but with demographics shifted increasingly toward older populations.
- Biomanufacturing will overhaul a lot of industries -changing where and how things are made, making some things ridiculously cheap, opening up new material types to large scale production, etc.
- Food insecurity will be effectively ended, but food systems will be changed substaintially.
- Fragile ecosystems and extinct species could potentially be restored, but there also could be an acceleration of destruction in many areas as "ecological capital" becomes more valuable.
- Bioterrorism could become a pervasive problem when every psycho with a decently equipped lab garage can create dangerous viruses on a whim
A tricky part of all of this is that there is massive potential to massively screw something up. In many ways recklessness will be rewarded and appetite for regulation is going to disappear pretty quickly when people see what the competitive advantage/disadvantage looks like here when it comes to fast movers vs slow movers. Not really an issue doomsday tech/disease/creature "escaping from a lab" per say, but rather just that the potential rate of change when this stuff gets commercialized is so huge it will be difficult for society to grapple with.