It seems to me that it should be possible to mount an actual camera in the gun now and have the system simply compare what it sees on the gun camera vs. what it is displaying on the screen. We have the computer power to do stuff like that now.
It won't work for retro-gaming, but it's a possible path forward for gun games on modern consoles.
I can't believe there hasn't been a good modernized design of a light gun. The lag and inaccuracy with the Wii style sensor bar stuff kills the experience. I used to have the Captain Power Powerjet XT-7 [1] and even that was a better than anything of late.