The Technological Singularity
The singularity is when AI surpasses the human level of itelligence. Nobody knows when exactly that will happen. Some believe it could happen in the next few decades.
I think it is the next logical step in human evolution.
Source: Wikipedia
Whatever the exact timing, it will be a really big event. It will probably be the most significant and important event in our history. The scary thing is that it could even result in our species becoming extinct. That is what some futurologists think might happen if we don't control the advancement of artificial intelligence.