They also once said it would be impossible to turn lead into gold.. I'm not sure what point you're trying to make.
I do think that getting photo realistic graphics will be possible soon-ish, but like Blackhand said, getting it to render in real-time is another story altogether. Also, even when we get photo-realistic graphics, we'll always find new part to the graphics to improve on visually, and then find way to improve computationally.
Hopefully, though, we'll get to a plateau soon, so that dev's can start thinking about gameplay and storytelling again.