Sony was leader in 2 generations of home console who have predict the PS3 will don't beat Xbox360 and wii it the same for nintendo if PSVita is a better handheld and game are better then 3DS nintendo will loose the leader.
And why talk about ds and psp battle it's not the same sroty then 3DS/PSVita.
Why some predict PSVita will don't have good game like PSP?
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