Demon's won't be forgotten because it was a launch game.
Anyway, looks like loading is damn great. Loading whole damn world in....1 sec. And actually, i've noticed that world is actually loaded when Ratchet hit the stone, immediately before flash animation and then new world shows up.
Eh, that looks great, but that looks like a lot of the asset hiding and color/lighting tricks that The Medium did, right? Like, this is the same stage, just with a Dark/Destroyed to Bright/Active look. (Look close and you'll see the same rails on the left, the big circular furnace-looking thing is there throughout, etc.) Probably R&C doesn't try to have "both stages" in memory at all times like Medium since it doesn't need to have them split-screen (the "dual-stages" thing is kind of a weird way of describing what that game did, but I would think it'd be the wrong way to go anyway in R&C since it's more open-world'ish instead of sectioned levels.) Sill impressive AF, but I don't know that it's loading an entirely dissimilar level in that one blip. (Like you said, the level actually changes and flashes in/out before it finally fades into existence.)
That's different from the purple Rift Tripping that Ratchet does, where he literally falls into a fully playable stage with just a blank void of super-quick loading to bring full stages into and out of playability. And actually, there may be multiple ways that purple Rifts work, because in the new footage, there's one
Rift you go through that two stages exist at the same time, but then the entire time, you're skating inside a confined road doing the same action, whereas previous trailers showed you going from grinding to riding to falling to fights in one series of Rift trips. (And we don't know yet how much you'll spend in any one Rift, or if it's just a trick where you're in a tiny bit of loaded level when you trip but actually playing a stage is mostly in a single level?) There are also the yellow Rifts that jump you from place to place inside the same stage.
It'll be interesting to see all the tricks that R&C Rift Apart uses, and take a look at what other games going forward might use of it. There probably won't be a
ton of games that use the multiuniverse idea of The Medium/Rift Apart, so the similarities and differences of those two will be neat to look at more on a technological and creative standpoint than this kind of "Better Game = Best Console" argument that comes out of this sometimes, but I think it's really exciting what Rift Apart is doing and it's looking to be a solid benchmark for next-gen to come.