Too early to say. There is so much we do not know. When will the PS5 release? That has a huge influence on PS4's sales. When will Nintendo release Switch successor? Also a big factor. What exactly is Nintendo going to do in the next 3 years? Again it is mostly a mystery.
So I am going to have to fill in the gaps. I expect Nintendo to treat the Switch as an NES. What I mean is that it will have ALL of Nintendo's 1st party support for most of its life. That means that Nintendo can experiment with new ips again like they did with the NES. This gives the Switch much more potential than any other Nintendo system ever. New Ips can sell a system much better than an established ip can 3 years down the road. Nintendo showed that they can make very successful new ips as Splatoon showed. There was a time when Super Mario Bros and The Legend of Zelda were considered a new series. What if Nintendo comes up with new ips like that again? Then we will have the second coming of the NES.
I am a toss up for now.If Nintendo doesn't go full stupid and does everything correctly then the Switch can match the DS's sales. If Nintendo goes full stupid then Wii numbers are more likely. However as the days go by I feel like the chance of the Switch outselling the PS4 gets higher and higher.
Also we need an F tier.
Edit: I think the Switch is more likely to win in the end.
