Yes, someone coming up with a superconducting material that functions at all temperatures. That will allow the development of batteries that hold a crap load of juice. But there's been no breakthroughs in that area since 1986.
I don't know about the rest of you, but I have this funny thing for my laptop called a power cord.
What I meant by my question is what, in thirty years when games may very possibly all be photorealistic unless the developers specifically intended for that not to be the case, will separate them by what we can actually see and notice? Graphically, why would there be any difference? Functionally, there's a certain limit to what we can see in a framerate, as well. What would effectively cause these fabled PCs of the future to be different in gaming... assuming heating issues aren't a problem... as is the case, now, really? When the software and hardware are advanced enough to make photorealistic games running at seemingly flawless fps's, what difference can we notice?