Holidays 2019.

Switch: 15M this year. 30M+ next. 45-50M at 2019 ending.
Xbox: 38M this year, 45 next, 50 2019.
So, 2020. Probably first half.
Unless they release a cheaper mini switch before that and manufacture lots of units. If so, I can see 25m levels per year.

I think some fans are being a little too optimistic here about the Switch. The thing only released a couple months back and there are already some getting upset just because people voted never. Switch is still very new and is still enjoying the fanfare of the hype surrounding a recent release. This is expected and thank goodness for Nintendo after the WiiU failure. However, this could very well taper off once the novelty wears off and I expect that it may very well do so. People have to remember it is a device trying to be a handheld as well as a home console. On the home console front I expect the appeal to not last very long as it is already quite outdated technology – and simply put the price will not justify it. I actually believe the XBOX One S has a slight advantage in the medium (and longer) term as there is a lot more room to cut prices significantly further. No one has even raised this point in this thread yet. Switch by virtue of being a dual piece hardware (console and handheld with display), means the room for a significant price reduction will be considerably constrained – same as WiiU. Also for people to predict that Switch to outsell XONE by 2019 or 2020 – that is way too optimistic. It will have to have PS 4 sales levels (of last couple of years) to achieve this – and we know that’s just not the case with Switch. The Switch will not be another Wii story. By then who knows there may even be an Xbox 4 or whatever they call it. If they decide to ditch generational categories, well than that’s another entirely different story.

I like my Switch, i think its a great system. However the X1 is still selling. We dont know the exact figures as MS isn't telling anybody. Saying the X1 is getting destroyed on sales is again speculation and not actual figures. Nothing is official.

As for Halo, the franchise mainline games can sell up to 10m units. How is Halo on the decline? because of one entry? Halo 4 sits on over 9m copies and possibly 10m  by now which outsold Halo 1 and 2. That isnt a decline. They had one of the best selling Halo games recently. Sure 5 went downhill mainly due to the direction and decisions which wont be happening with Halo 6. I never said Halo will outsell Pokemon. However its a juggernaut franchise that with protential can sell double digit millions and will push Hardware.

Remember the Xbox also has massive Xmas sales and is attractive for the 4k market which will be big in the next few years and houses the big 3rd party games. Switch will sell well for awhile however its New, its still selling based off hype and the fanbase. X1 is in its 4th year, its sales will start to look small by now however there are heaps of reasons for them to raise. As an over the top example - Sea of Thieves might be the next Minecraft, we dont know. All i can say is dont base your judgment off the sales charts when one number isn't even confirmed by MS.

I see Nintendo releasing a new system in 2021 which will replace the Switch while X1X will continue to push X1 sales same goes for X2. Thats my prediction.

The most logical reason MS aren't releasing numbers is because the numbers are not good. If Xbox One was doing well, they'd be bragging about it.

The sales of Halo games have been in decline since Halo 3 in 2007, with each entry selling worse than the one preceeding it. Halo only crossed the 10 million mark once, and those days are long gone. Neither Halo 6 nor Sea of Thieves will alter Xbone's trajectory significantly, just like Halo 5 didn't, Gears of War 4 didn't, and Quantum Break didn't.

Xbox One X is too expensive to make a big difference, people will just buy the PS4 Pro instead. While Switch has carved out a niche for itself, Xbone has to compete directly with PS4, and is getting its arse kicked.

And why would Nintendo replace Switch after only 4 years? MS are the ones with a motive to replace and move on sooner.

Depends entirely on how fast Nintendo can produce these things.

I think you underestimate the DS fans. If Nintendo doesnt make a new secondary handheld during the generation of the switch and keeps the devs who work on the DS working, they can have console/ handheld quality games. This will definitely push Nintendo beyond Microsofts potential. 

I vote late 2020. Switch is going to sell 15+ million for the next four years. (Unless something stupid happens)
The gap is like less than 30 million now so it shouldn't take too long.

The Switch will get handheld and console 1st party support. Nintendo is basically throwing their entire weight on this thing. I also expect 3rd party support to grow as time goes on. So the Switch could outsell the Xbox One even sooner.

Just to close the gap (circa 26 million) in three years, Switch would have to sell on average over 160,000 units extra per week. On average XB1 sells 150k per week. So to outsell XB by mid 2020, we would need to see 300k+/w or 15 million units per year ... considering that XB will keep selling at the current, consistent rate.

Because Switch is not a handheld for nintendo, but a home console.  

I'm pretty sure they will show a real 100% handheld console in 2018/2019.