Hi Darren, always good to see you here!
The scenario in which a superintelligence emerges and prevents us from switching it off is one of the most frightening, indeed! I'm currently writing an article about the reasons some people (even remarkably intelligent people) fear the future of AI.
I think AGI is still very far in time, as you say, but it's never bad to be careful and assess the situations we may encounter! :)