Only time will tell. It's still very early on, and the trend may or may not catch. Right now, no, it will not replace your smartphones. They make great companion gadgets for some people, but the functionality is still limited and battery life is the main concern with many models. As technology advances and components get smaller, they'll be able to fit more into these smartwatches, allowing them to do more and more and possibly compete with mobile phones, but I'd say that that is at least a few years down the road.