I'm not sure about AI wiping out humanity, but it will definitely change the world as we know it today. Over what time horizon, I don't know, but it could be even more dramatic than the advent of the internet in the way that it impacts our lives.
Somebody mentioned schools earlier as an example. There is no AI currently available that can detect with confidence if something has been written by AI, and honestly this is an entirely pointless endeavour. There are companies like Turnitin who claim to have created such an AI but if you look under the hood you'll find them riddled with disclaimers about their efficacy. Because the truth is that all they are doing is looking for the kinds of common formal writing patterns that an AI would use - they are thrown off by simple things like deliberate grammatical errors or telling the AI to "write in the style of somebody else". As well as this, a sufficiently good human writer can write in a style that these AI detectors might falsely interpret as being written by AI. Think about it, the AI doing the writing is designed to mimic humans to increasing magnitudes of accuracy that will only get better with time. Therefore the space for detecting the differences between human and AI writing is shrinking exponentially to the point where it is now effectively impossible to distinguish the two.