Anyone who has an iPhone or Android handset can tell you that the standard method of using a keyboard and mouse for interacting with a computer is starting to be replaced with more natural and intuitive interactions. The iPhone has popularized the pinch-and-zoom and other finger based gestures that are commonly used on multi-touch devices, and Android has done a lot of work enabling voice based input to prevent having to enter text manually into the phone. Many smart phones use voice or touch for creating Natural User Interfaces on hand-held devices, but the transition to NUI in your home or office computer has been much, much slower.
On desktop and workstations I think that we won’t ever fully replace the keyboard and mouse, as they have proven to be highly configurable input devices with much better accuracy and precision and much lower cost than any alternatives. Over time though there are many cases where using speech or touch on a device larger than a phone makes sense. Microsoft started initially with their Surface device (aka the $10,000 coffee table), and has taken all that experience and added full multi-touch support to Windows 7 and Silverlight (when run on Windows 7).
It will take some time for the hardware to come down in price and be available in low-end consumer devices, but already you can find reasonably priced multi-touch desktop computers such as the HP TouchSmart line of all-in-one or laptop computers. These are designed to be used in a kitchen or as part of an interactive display in hotels and businesses where using a keyboard and mouse is not very effective. Microsoft hopes that lots of companies will start using these to attract customers or extend their brands, something that the Hard Rock Cafe has already done quite well.
Besides the hardware, another major factor holding back NUI is the ability for developers to create usable interfaces that compel users to let go of the keyboard and mouse and start using their fingers/voice instead. If you are a software developer, a UI designer, or just interested in seeing where human-computer interactions are heading I highly suggest watching this video from MIX 2010 about designing NUI on Windows. There also is a shorter follow up video on Coding4Fun where Brian Peek interviews NUI expert Joshua Blake.