lucidium on 24 April 2014
i dont really consider handhelds to be the same kinda "generation" as handheld consoles, instead they have their own generation cycle.
3DS would be 4th gen (if you dont count gameboy variations as different generations), with gameboy > gameboy advanced > ds > 3ds
Vita being 4th gen also, with the psp starting in 3rd gen handheld, psp > psv
