Probably best to have these connected with cables though I don't know how long the cables could get while maintaining performance.
The point is not really "how can we do this with cables" the point is more what new possibilities doing it without any cables bring.
Enough bandwidth? Well, I'm sure that could be worked somehow. Maybe double up the transmitters. However, I'm not even saying it is possible yet, just if it is possible what one could do to utilize this concept for silence. If it is not really freezable yet, it probably will become rather soon.
Hard drive being near you can be a good thing, if the transmission technology is fast enough. Portability of huge amounts of important data for example. If everything were wireless, you could have your hard drive plugged in where ever, assuming the wireless communication was able to communicate clearly with it.
It doesn't really matter in this example where the hard drive is though, since the point is more separating the heat producers (cpu/gpu/psu) from the fairly silent passively coolable components (sound, dvdrw/cdrw, mouse, keyboard, monitor).
Everything is now possible to communicate via digital. Therefore anything could be communicated through wireless I would think. DVI video, spdif sound, etc. Of course this could also be done digitally over cables, if one were so inclined. Cables however remove any portability this approach might have.
Having a universal communication technology such as maybe Bluetooth for everything you could have a transmitter at the cpu/gpu/psu sending to a receiver in the house, which then retransmits to everywhere in the house. Then printer, monitor, keyboard, everything could be anywhere and be hooked in.
The key idea I'm looking at here is the possibilities that separating the heat/noise producing components (cpu/gpu/psu) from the rest of the system wirelessly could bring.