Interactive Revolution
When you look at the three games consoles this generation the most mysterious, pre-launch, had to have been Nintendo’s “Revolution”. There was a lot of speculation to what this machine could actually do and some of the prospects really gave an insight as to what the future might eventually hold for gaming. The most highly speculated theory was that it was going to be a virtual reality headset. Mock ups started appearing on the internet very similar to this:

The future?
Of course the mystery was then revealed as wireless, motion sensing controllers, which is still a major leap forward from standard wireless controllers.
Sony have started looking into the possibility of fully realised 3D gaming environments and this was one of their most recent demos:
http://arstechnica.com/gaming/news/2009/01/ces-2009-sony-teases-with-high-quality-ps3-3d.ars