PlayStation 4 - 200 Million
Xbox One - 70 Million
Switch - 120 Million
3DS - 75 Million
Switch is the hardest to predict, it could do 40 Million left as is, or it could do 240 Million if they go full on mobile in future iterations. 3DS should slow way down/stall next year. Xbox will do better than people expect, but Windows is the future of gaming in the Micosoft ecosystem. PlayStation will have further iterations of PS4 reaching even higher and lower tiers, making PlayStation 4 a choice for people wanting a set top box, to those that want the best performance available, but don't want a PC.
Based on your prediction, do you suppose that PS4/XB1 will have another revision somewhwere around 2019-2021 instead of proper next-gen? Because if they won't that's highly unlikely that PS4 will sell that much. And your statement about Windows being the future of gaming in MS ecosystem... While I agree with it, I still don't see it coming in the near future. They've got a long way to go. I doubt Windows 10 will be able to become a decent gaming platform in the next 5 years. MS has made very little progress since last year with it. And they basically need to kill off Steam probably if they want to use Windows 10 instead of Xbox as their main focus. And the problem with MS is that they are some kinda impatient so they can give up on that idea just like they did with GFWL.