I don't know why people are SO confused by the Switch. It is a 9th gen console. That doesn't mean that you can't compare its sales to the PS4 or that it doesn't compete with it. This isn't the first time this has happened.
During the 1st gen, the Odyssey came out 3-4 years before its competition. Same gen. During the 2nd gen, the launches of HW was spread out over 4 years. Same gen. During the 3rd gen, the NES/Famicom launched 2 years before the Master System and 3 years before the Atari 7200. Same gen. During the 4th gen, the Turbo Graphx launched 3 years before the SNES. And the Genesis launched 2 years before it. That doesn't mean they were of a different gen just because they competed against the NES and Master System at first. During the 5th gen, every other system launched 2-3 years before the N64. Again, same gen. During the 6th gen, the Dreamcast launched 2-3 years before the other consoles. Same gen. If the PS5 launches either in 2019 or 2020, which it will, then it's the exact same thing.
Remember, what happened last gen and this gen, where they all launch within a year of each other, isn't really the norm.
