Not only they will – they already are, if you want them to be!
Voice control is not too complex. It requires a microphone and a program able to recognize the human voice and understand it. Now, this is the hard part. Our human brain is very flexible: we hear the same words said by different people and recognize them, pretty much. But the “sounds” those people produce are very different! Someone maybe has a high-pitched voice, someone else has a raucous one, someone has a weird accent or a speech quirk… for computers, telling the difference can be very hard, and this is why voice control is hard to obtain. But not impossible. The new XBox console, the infamous “XBox One”, for example, will have voice control commands that allow to turn it on and off, among the other things. There is a program called “Dragon Naturally Speaking” (a bit expensive, in fact) that allows the user to speak and “dictate” to the computer – it can be used both for computer control and for dictating instead of writing. However, before you can use it, you need to “train it” by reading some text with your voice, so that it can get used to it! Of course, this is still an imperfect technique. To have an example of how hilariously bad it can fail, you just need to take a YouTube video and put on the “automatic captions” – those are supposed to be a voice recognition of what is said in the video which then is translated into words, but they seldom have anything to do with what is actually said!
However, I don’t think computers will ever become fully voice controlled, for a simple reason: voice control is tiring! I used it when I was studying, thinking that “dictating” my notes would be easier than actually writing them, but I was soon disappointed. Not only because the program would continue making mistakes that I had to go back and correct, but because my voice got exhausted after a while. You need to speak every word loud and clear, and always with the perfect pronunciation. It’s not like talking to another person at all! So, in the end, it will probably be always more natural to just use a keyboard – easy, fast and effective. But voice control will be available as an option – for example for people who can’t use a keyboard due to some handicap – and will always improve from now on. Maybe in a few years it will be good enough that talking with a computer will be just like chatting with a friend!