Fuchsia OS is a new operating system under development by Google that could run on multiple devices; from smartphones to tablets to personal computers, including home gadgets and other embedded devices. It sounds ambitious, but we don't really have enough information to draw many conclusions. The project is still early in development and Google isn't saying much about it. As far as replacing Android, that doesn't seem to be the main intention; at the very least, it's not going to be implemented within the next five years. So as an Android user, you really shouldn't be worrying about this for now. But if you're a tech enthusiast, I do believe this is worth your attention, as it could have a huge impact in the industry. Google would have their own unified system running everywhere and they could keep full control over it. Of course, maybe this will flop horribly and you'll never hear about it again. It happens a lot with these sorts of things.