I don't know how the gamecube sold just 21 million, but i think the vita can easily surpass that, it's still an infant system really. At least 50 million is likely, but i think it could reach PSP lifetime, which is 70 million now
Xbox One, PS4 and Switch (+ Many Retro Consoles)
'When the people are being beaten with a stick, they are not much happier if it is called the people's stick'- Mikhail Bakunin
Prediction: Switch will sell better than Wii U Lifetime Sales by Jan 1st 2018