Hard to say imho. It will mostly depend on the sales performance of the PS4.
My current guesses for the end of gen sales are:
WiiU: 20m
Vita: 18m
3DS: 95m
PS4: 120m
But I'm really unsure about the PS4. I think that it's possible that because of cloud gaming there will be no real successor to the PS4 and thus the PS4 might be on sale for a very long time. On the other hand just the opposite might happen. The current gen systems are somewhat underpowered and it might be neccessary to make this gen a shorter one with a release of all next-gen systems by 2018 (especially if VR-gaming is a success it might be reasonable to release the next-gen early on); this in turn would of course hurt the sales of current gen systems. So anything between 75m and 150m for the PS4 is possible. And how would we treat a streaming-only "PS4"?







