SS tier is for those consoles that sells over 150 million. It did not specific "how much more" simple because there is not another tier above that, or at least there is not one yet.
DS and PS2 are very close in sales, and both are waaaaaaay head any other consoles, no console outside of those 2 reached 120 million units (PS4 was looking very likely to surpass it but now we are not sure if it will), and those 2 sold +30 million more than that.
For being SS tier, Switch has to sell 150 million units, which i think is very likely. But as of now i don't have plan to make another tier for it, unless it sells WAY better than DS and PS2...
How much better? we'll see i guess, 200 million is DEFINITIVE another level and deserve his own tier. Maaaaaaaaaaaybe even 180-190 million would be enough for another tier... if it sells 170 million, i don't think it'll be another tier, it would still be SS like PS2 and DS.
