Need help with career path

Hi, I have almost 8 YOE in software development. I was in my comfort zone and spent 6.5 years in a service based Indian MNC on a legacy project, where I only did what was assigned. I don't think I have good skills in the technology I was working on. Then I switched and I wasn't informed but when I got into the new company which did pay me much better, my technology got changed. Now earlier I was working on a very highly used technology, but now I am on a niche technology which is less used and might disappear in say 10 years. I am worried about the future. I don't know if I should go back to the technology in which I was working earlier (C#.net), or learn a newer tech like data science or AI and try to start fresh or continue with the one I am working on(a Telecom billing solution). Can you please suggest to me the path?