The 3DS and XBONE are both pretty much at saturation now, I don't think the 2DS XL and XBONEX will make much impact. PS4 sales are being canabilized by gaming PCs and mobile, but still 90M is quite strong. Switch will have a good holiday season for sure, but after that it won't be until the next mainline Pokemon game appears on Switch before it reaches saturation. If it comes out in 2018 I would revise Switch sales up to 60M+ because of the momentum but I bet Nintendo won't do that. Switch also needs a price cut in 2018 if they want to compete well.

3DS 73M
PS4 111M
Xbox One 67M
Switch 81M

3DS: 76M
PS4: 115M
XBOne: 65M
NS: 110M

Oh, fun!

3DS: 75m
PS4: 120m
Xbone: 55m
Switch: 100m

PS4: 110m; it's going to continue selling very well, but don't think it'll be PS2 ubiquitous

Switch: 80m; too early to tell, could very well be higher, depending on whether it can recapture the 3DS audience

3DS: 75m; the system has peaked, plus Nintendo will be keen to move support to the Switch after this year

XBone: 45m; they'd be lucky to get this high, will probably try to cut the generation short, again

The paradox

PS4: 102 million
Xbox One: 48 million
Switch: 83 million
3DS: 74 million

Dang, a lot of you are way more optimistic about Xbox One's future sales than I am

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.

The PS4 prediction may be a bit high. It will outsell PS2 lifetime, but maybe not quite 200 million. I see extreamly strong legs once the 7nm super slim model arrives at $149.99. With OTT TV services growing and the Set Top Box becoming a staple of every TV. PS4 will be the ultimate device for any room in the house for many years to come.

What is wrong with XBO though? It will be in the high 30 millions by the end of the year as best we know, and we are on the not even at the half way point for sales. Why would it not roughly double over the next 4 years? It will benefit from the surge in OTT TV as well, and it will have a 7nm revision as well which will make it easily one of the best options in the market of Rokus, Amazon Fire TV, and Apple TV devices.