Smartphones have been growing at an eclectic rate over the past decade. When a new technology like this comes up there is a lot of speculation on how this will impact existing technologies. This has definitely impacted the sales of PCs and laptops.
However, overall they have not replaced laptops but have become a complimentary device. Now we have four ways of connecting to the internet and running applications, PC, laptop, tablet and smartphone.
Each device has it’s place for what it is good for. However, like the way that desktops did not disappear when laptops arrived. Laptops have remained when smartphone/tablets have arrived. Sales have been impacted but you won’t find people doing away with laptops completely.
The exception to this is tablets such as the Windows Surface PC. This device attempts to replace the laptops with a device which is a slightly thicker than average tablet. This type of configuration is probably what is giving the most competition to conventional laptops.
At the other end, laptops have also started to become more like tablets in terms of their components. The new Macbook is a good example of this. It has only a small tablet like motherboard which holds all the components, even though the form factor is that of a laptop.
I think overall the hybrid tablet/laptops are mildly successful at replacing conventional laptops. The main drawback of such devices is upgradeability and ease of repair. Such compact devices don’t have many replaceable parts but have become more modular. If something does go wrong in these devices, they are likely a throw away and replace.
In conclusion, conventional laptops still offer a good value/performance proposition. How long this will last is up for debate. With changes in processor speed, a tablet or smartphone may be able to match the performance of a laptop.