If we're talking physical game sales only (which we seem to be), Switch will likely not touch 1 billion. Think of it. The Switch will probably sell 100-110 million units. That's a software tie ratio of about 10-9. I don't see most Switch owners reaching that threshold, especially only including physical games. Switch will very much hit 700 million, as its already over halfway there. Also keep in mind that we'll get at least 250-300 more physical Switch games in its lifetime. I'll predict 750 million software sales.
Lifetime Sales Predictions
Switch: 161 million (was 73 million, then 96 million, then 113 million, then 125 million, then 144 million, then 151 million, then 156 million)
PS5: 122 million (was 105 million, then 115 million) Xbox Series X/S: 38 million (was 60 million, then 67 million, then 57 million. then 48 million. then 40 million)
Switch 2: 120 million (was 116 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