Wii U: Already have one, very happy with it.
PS4/XBO: As soon as there are around 10 game that i want to play as much as Bloodborne (which is the first until now). Simultaneously, whenever Silent Hills or a good FF XV launch, i will make my decision and buy it, even if there aren't those 10 games yet.
After picking one of them, i will not pick the other.
PSV: Most likely not, but If i do get the PS4 than the PS+ free games and a cheaper price could do something about it.
3DS: Already have one.