Probably a 9 because of some first-party games that are amazing like Super Mario Odyssey. For all the Switch's faults, there are some stellar first-party games (new and ports included).
I can't give a 10 right now because of the garbage online that we pay for, lack of Virtual Console. JoyCon drift, etc. If some of those things are still there in the end but the Switch gets better in some other ways, I might give it a 10. For reference, I don't think I'd give any video game console a 10/10. Even some of my other favorites like the PS4, 3DS, and GameCube still have some notable flaws.
Switch is 4, and still only in the middle of its life. For reference, the Wii U was basically dead at this point in its life. The Wii wasn't dead, but was about to decline.
Lifetime Sales Predictions
Switch: 144 million (was 73, then 96, then 113 million, then 125 million)
PS5: 105 million Xbox Series S/X: 60 million
PS4: 120 mil (was 100 then 130 million, then 122 million) Xbox One: 51 mil (was 50 then 55 mil)
3DS: 75.5 mil (was 73, then 77 million)
"Let go your earthly tether, enter the void, empty and become wind." - Guru Laghima