Ummm werent we promised zero loading times? Or that is Sony's promise?
This is a demo based on a game that was written for xbox one, it does not take advantage of newer read/write technologies for NVME SSD drives. The game engine still assumes its a standard hdd, simply a faster one, hence the reduces loading times. Now this is quite the impressive demo with significantly reduced loading times, yet do not expect the impossible. There is no such thing as no loading times in game development. When I introduce a new scene in our game, I have to load all the assets and files into the scene and that takes a little bit of time especially on xbox one hardware, right now we use a lot of tricks to bridge the loading times. With the new gen we can simply reduce a lot of these tricks and if we really optimize our games for those new ssd drives, loading times again will be significantly reduced. In my opinion the thing that bugged me the most are the streaming capabilities of those standard hdds.
So to summarize, for last gen games simply played on next gen, the zero loading times thing is very hard to accomplish, since there is no code optimization. For true next gen games developed from the ground only for the next gen, that could very well be the case, tho I dont think its going to be no loading times, but very short ones.
