I like this question. Let's see.

(1) I'm pretty confident that ethernet is on the way out. About ten years ago I was getting my first computer, and I decided not to get a modem. My parents thought I was crazy, but I was right. Ethernet is a safe guess to be a thing of the past much sooner than ten years from now. Let's get more ambitious...

(2) Relatedly to the prevalence of wifi or other always-available data connection sources, the increased reliance on cloud computing will have some dramatic effects. I think that USB thumb drives are going to be pointless very soon; just put what you want in your dropbox. I rarely use mine already. That one seems close and too easy, too, so I'll make a more dramatic pick in this genre as well: I think that in 2020, operating systems on hard drives will be a thing of the past. Personal hard drives in general will be much less useful, as we'll have no need to store our documents, or even our applications locally. The nervous among us will keep backups locked away in closets, but we'll store everything in the cloud day-to-day.

(3) This one's further out there. I don't know if I'm right, but I'll go ahead and predict the demise of the laptop computer. Desktops will always be there, because it will always be easier to make more powerful machines if we don't have to worry about size and weight. But as smartphones and tablets get better and more sophisticated, I think the value of the laptop will eventually be much more limited. (Because of the increase in cloud computing, it'll be much less important to have your own computer traveling; if you need something more powerful than your phone or tablet, you can log into your friend's desktop, or a public one, and have all your applications and files and settings, just like at home.)