I think I know what's going to be the next big thing.
Real 3D "movies" of real people that you can watch from all angles as if they were there with you, with positional tracking, captured with multiple scanners, played back thanks to Carmack code compressing the hell out of that 4D data to be accessed and streamed to the GPU as needed depending on where you look.
Not 3D 360 degree movies... not real time rendered fake stuff. Real people, like they are really there with you.
Not whole stadiums, just one person. Also movies as they scan actors and put them in CGI spaces anyway. And as we take our loved ones to be scanned so we get to keep their memories forever, maybe we'll get that feeling our grandparents must have felt when they took our parents in for their first photos.
No physics, no dynamic lighting, no simulations, no artificial intelligence, no destructible environments... just predetermined, recorded stuff streamed using the information of where you are looking and the prediction of where you will be looking, which Oculus is already doing.
Yes, it's a whole lot of data. But all types of work andoptimizations Carmack has done and let us know he looked into in the past years should translate so well to this. And he has supercomputers with special purpose computing units at his fingertips, with lower level access.
What we have seen so far is nothing. Knowing that is what makes waiting hard. It's like you knew the photo was coming to town and everyone is excited but you know they are doing this thing called "movies"and you believe it will be big.