Will a Tablet ever take over PC's? It depends. I own a tablet (got it as a gift) and several computers. I also sell and fix tablets. Personally, I see my tablet as an extension to my computers; I'll use it to check my e-mails, to watch videos on and play games with. Sure, I can do all these things on my computers, but it's easier to do it on my tablet.
These days, you can even get hybrids (convertibles) like the Asus T100, HP Split X2, Microsoft Surface PRO 2.
Technically speaking, the most advanced tablet will never be as powerful as the most advanced computer.
However, people like tablets. In the store where I work, I sell twice as many tablets as I sell laptops/desktops/all-in-ones.
People like Facebook-ing on the sofa, watching videos on the bus, playing angry birds in the bathtub and so on.
So to answer your question, will tablets take over PC? It depends.