No way RatchetnClank is a launch or Launch window title. The footage from this past June said Pre-Alpha. That means 12-18months out, also add Covid to the mix. Maybe September 2021, Maybe.
A lot of the time, demos are made months in advance for game shows, while the main game is being worked on. For example, when I was QA for Neverwinter Nights 2, we had a separate build that was specifically an E3 demo, and we had to test both the demo build, and the final game. The game released a few months after that, even though the demo was using an earlier version of the game at the time of its public showing. It's more than possible that the demo shown at the PS5 event in June was indeed an earlier alpha build, while the team was still hammering away on the build of the main game. I'm not saying the game is a launch title, but considering that Insomniac has two teams, both of them a pretty healthy size, I wouldn't be surprised if they're targeting 1st quarter 2021. Like I said in my earlier post, I think it's more about scheduling releases to not bump into each other too much than about whether the game is ready for launch.
And believe me, developers will take whatever extra time they can get on their games if possible. But not gonna lie, having Spider-Man, Ratchet, and Demon's Souls among others available by Holiday 2020 would be quite the stocking stuffer for a lot of people. It's a nice bit of variety for launch; open world mega-popular game, family friendly action platformer, and hardcore RPG, and that's just three games out of who knows how many launch titles. I imagine Ratchet and Spidey wouldn't cannibalize each other, though there's bound to be overlap (I mean, I'm a
huge Ratchet and Spidey fan, so if they were both launch, I'm getting both at launch; ditto for Demon's Souls).
Personally, I'm making sure I have at least a grand saved up for the PS5 launch, just to cover hardware and software/accessory costs.