Call me crasy(sorry missing letter) but Vita will catch the 3DS and will sell much better.
You would like to know why ?
Simply because Vita will last forever ( i mean for 2 generations), it's the final sony handheld so sony will keep it alive as long as dev will make games for it, and since i doubt the 4DS will be more powerful, Vita will compete against it.
I tell you, Vita will become the cult handheld for 10 years.
So, crasy ?
Predictions for end of 2014 HW sales:
PS4: 17m XB1: 10m WiiU: 10m Vita: 10m