Ok a lot of thought went to this thread. I can definitely see your point. I too see this as the upper limit as well. However it would assume that Nintendo does everything right as far as 6 years from now. Which is unlikely but possible.
Anyway the Switch having a monopoly on the handheld market its a big deal since that mean monopolized 3rd party support. If you want to make a handheld game you must make the game for the Switch. Nintendo handhelds usually sell amazing and the Switch seems to follow that trend.
Home Console wise is a bit tougher. The Switch seems to be focused on lapsed gamers right now. However I expect that Nintendo will slowly add other gamers. I can see them grab gamers who do not value AAA gamin. (Which there are a lot of.) With great 3rd party support it can help grab more non-nintendo folks.
Anyway I give the prediction a 10% chance. I think it depends if Nintendo makes any mistakes. Also the Switch winning 9th generation has a chance of happening above 50%. Unless Microsoft decides to give up on console gaming or something like that.