Nintendo have used 2 of there big cards already with Mario and Zelda this year. Pokemon and Metroid 4 become there next hand however we forget X1 still has Halo 6 and Sea of Thieves as there next big line up. So the way its going i see 4 years if MS next hand doesnt do well which i daubt will be the case. So expect big numbers from X1 next year.

It won't. Nothing can beat the power of the X.

Power is fleeting. Great games last forever.

X has the former. Switch has the latter.

We'll see about that once the X1X launches.

I think the X is going to "re" sell to Xbox fans very well, so it should give hardware numbers a decent boost, though it will be interesting to see if it significantly increases software sales or if it mainly just keeps those in the xbox family entrenched in the xbox family. With that hardware boost, especially in this launch period where I think we'll see the xbox faithful go wild for it, I could see the Switch catch it in about four years. Of course, if the ps5 ends up coming in 2019 or so, I expect MS to quickly move on to the Xbox 720 or Xbox One Two or whatever they have planned, so sales would tank then and Switch could catch it sooner. 

Still, I'm bullish on the Switch, so I do think it will surpass the xone eventually. The PS4 I'm not as certain. It will obviously beat it handily in Japan, but I don't know if Switch is going to be able to do the European numbers necessary to catch up to Sony's lead. It's already at $299, and so price cuts aren't going to be quite as effective for it as they were for the $399 systems, I think. 

If we assume that Xbox One sells 8 million this year and switch will end up selling 12 million, then we will have 36m xboxes versus 12 million switches by the end of the year. In 2018, Xbox will probably end up at 44-45 million while switch at 26-28. So, 2020 will be the earliest when switch will overtake xb1. Probably even in 2021.

P.S. Though it is hard to predict because there are many factors that can change the sales pace of both consoles. Switch can have a huge boost when Pokémon game releases. Also, we don’t know anything about MS first party situation which can increase Xbox sales or decrease if MS continues not investing in first party like this year. Also, let’s not forget that MS as they said themselves decided to go generation less way so the next Xbox which will compete with ps5 can still be a part of Xbox one family and then I doubt that switch will be able to overtake it ever.

X1 is 35-36 millions so it will take some time, I think 10 million switches this year is a safe bargain, ok My guess is 3-4 years

If Microsoft can make the Xbox One family span multiple generations, then why can't Nintendo do the same for Switch? Nintendo already has a precedent for this with the Game Boy line, which lasted 12 years before getting a full successor.

Aside from being a halo product, I don't expect much in the way of direct sales with the XxX.

I think we could see the Switch, or a version of it at the price of about $200 before the end of 2020.
That would be a large driver in sales especially combined with Pokemon, natural celebrity endorsement, and enhanced visibility.
The Switch is finally the console that could potentially break into the mainstream in a good way for the industry (ie, not like the Wii, or as a media hub like the PS2).
The weakest part of the visual design is how it looks in the dock, everything else (like a big vent at the top) can and should be nullified by a Switch revision.

Anyway the numbers are wild guesses that I came up with on the spot.