Tablets are not taking over from laptops
They are simply gaining ground where laptops were inappropriately used in the past. :D
That includes being left lying around in the lounge for casual surfing and map and contact info lookup etc while talking on the mobile. It includes ebook reading.
Tablets don't really excel at any one thing, they just do lots of things reasonably well. Being a PC (as in computing things, cpu heavy data processing) isn't one of them. Conversely, PC's can do lots of things, but generally fail at looking neat and tidy in the lounge, being held in one hand while the other types while you stand in the kitchen with a phone between your head and shoulder; battery life (availability) without a wire, being light enough to give to a child to hold in one hand, having a decent rubber casing in case you drop it, etc.