So even you yourself remain uncertain ... (And it's not just about X1X itself, it's about the X1 family together.) 

Lol, wut kind of statement is this. Yeah I'm "uncertain" I'm not an all seeing prophet. I know it's about the X1 family. Without official numbers it's hard making a prediction.

I'll go with early 2020, as I think that 3 years is about the quickest they can do it. I don't think they'll be faster than that.

Don't have to be, you could always have a confidence range but just as you try to challenge those who predict it will take 4 years you aren't even willing to put yourself up to some scrutiny to lay out your reasoning for your own prediction either ... 

Here is what the Xbone sold by year with lifetime sales in parathenses

2013 : 3 Million (3 Million)
2014 :  7.9 Million (10.9 Million)
2015 : 8.6 Million (19.6 Million)
2016 : 8.3 Milllion (27.9 Million)

Switch sales for the year so far is 5.3 Million
So if I made rough estimates future Xbox One sales could look like this

2017 : 8.3 Million (36.2 Million)
2018 : 8.3 Million (44.5 Million)
2019 : 5 Million (49.5 Million) (This year really depends on a Xbox 4 relase or not)
2020 : 4.5 Milion (55 Million)

Now let's  compare the Switch 

2017 : 14 Million (14 Million)
2018 : 17 Million (31 Million)
2019 : 19 Mllion (50 Million)

Now assuming the Switch gets more support as time goes on and the Xbox One contiuing with steady sales. The earliest the Switch can pass the Xbox One is very late 2019. The latest is 1st half of 2020. Honestly if Microsoft release the Xbox 4 late or doesn't release it at all than post pone everything I said by a year. 

Well that's quite the leap in logic. Admitting that you don't know for certain how long it will take > Not willing to take scrutiny. Although my original post might need some editing looking back on it , but damn, you didn't need to be that harsh about it. My prediction is already in my original post plain as day. I'm not hiding my OP. Criticize it if you want.

But considering the XB1 has sold anywhere from 60k to 100k on a weekly basis, and also conisdering holiday sales, anywhere from 7-8.5 million is likely this year. Then the Xbox will be at about 37-38.5 million by the beginning of 2018. All things considered I think XB1 will begin 2019 (as in, in march time) with about  44 or 45.5 million. From there I expect sales of 5.5 million, it will be a slower year for Xbox in 2019. This will lead to 49.5 or 51 million sales as of march 2020.

Nintendo's predictions have the Switch selling about 13 million in it's 1st year. I think it might do a little bit better than that but just on the safe side i'll say it will sell 13 million. The Switch is currently outpassing the DS and 3DS, although iirc not outpacing the Wii. Part of that is due to both those systems launching with continous problems, but one thing that is always noticably is how all three of those systems had a huge growth in their second year. Switch will most likely do 18 in 2018, with 19-21 million the following fiscal year, giving it a total of 50 million or 52 million by March 2020. Which means it will either beat Xb1 exactly 3 years after release, or some time later in 2020.

I realize though that this is just my prediction and that it's not necessarily how things will play out. Maybe four years isn't as ridiculous as I originally thought. 

Perhaps 4 to 5 years would be possible? That is if the Switch continues to have great sales and doesn't lose interest. Whether the system will continue to be successful, I think it's too soon to say if it will or slow down once demand has been met.

3.5 years or less.

Also, who's this Alson you keep speaking of?

Thanks for pointing out my mistake good sir. It will help to improve my poor expertise in the matters of the english language.

I think 2018 might be a decent year with 2019 being a massive bust, 2017 would have been a much larger failure, but the Xbox One X should help it out, especially over the Holiday period.

2018 could potentially have: Crackdown, Halo 6, Forza, Gears 5, Sea of Thieves, State of Decay 2, Ori and the will of wisps and maybe a few other titles which  might get announced before then, the Xbox One X might help improve numbers slightly as well.

I just don't see anything of value for 2019. No new hardware, no new big games due to multi-year development cycles...

With that, Switch is not showing any signs of slowing, if Nintendo sorts out it's supply drama's, they might do significantly better than current projections would hint at.

I'm going to go with 4 years. Only because 2018 could be better than expected, with the potential for it to blow out to 5 years if Nintendo doesn't get supply under control.