I don't know,it's not that people wasn't interesting by system itself it just that they didn't find the games they want on it,if Sony is confident that they will succeed to attract the 3rd party they will definitly make another one
PS4 - over 100 millions let's say 120m
Xbox One - 70m
Wii U - 25m
Vita - 15m if it will not get Final Fantasy Kingdoms Heart and Monster Hunter 20m otherwise
3DS - 80m







