The differences will be subtle, but important. Voice input and control has gotten good enough that it's now generally usable. Voice output is less likely in the very near future, but I suspect it is inevitable. In the US, the Americans with Disabilities Act mandates the use of accommodations for the disabled. As the US population ages, there will be more pressure to make computers easy for the blind to use.
Visual input is a wildcard.
I talk about above is fairly processor-intensive. You won't be able to run it on your old 486. But you can begin to imagine how the different pieces could work together. If I'm sitting at my system and new mail arrives, I can gesture at the mailbox icon, and the system will show me the new message. If I get up from my chair, the camera notes that I'm not there, and a voice alert tells me that another message has arrived.