The system currently stands at 29 million according to VGChartz numbers, after 3 and a half years on the market.

Do you think it will end up selling more than 50 million lifetime, and why/why not?

Yes, and quite easily in fact. The total sales LT should be well over 50m, something like 57-58 m LT.

Edit: the Xbone ain't going anywhere for at least the next two-and-a-half years, and if it sells at the rate it's selling currently at the whole way through, it will breeze paSt 50m 

Where did you get the 32 million number from?

We're roughly halfway through the generation. I'd say that's a pretty safe bet. 60 would be the more interesting number.

Yes! It will do half of what PS4 will have!

Needs to average 6 million for next 3 years.
Seems that 50 million will be achievable. One x will help a little(2 million a year)
Next xbox will probably launch after 2020,

Tough to say. Doesn't it usually sell 7-8 mil a year? Add the fact it doesn't have a new halo or gears coming out this year, and a $500 pro version coming out, I see sales beginning to slow considerably. Especially now that switch is outselling it even. So let's say the 30ish million number is correct, it should be around 36-37 million by year's end.

2018 should see sales reach 42-43 million. 2019 might get close but probably fall short by a million or two before the next Xbox launches. That's my two cents on the matter.

Edit:  I see the X doing very little to nothing for the install base in any meaningful way. Especially with PS4 slim at $249-$299, Switch at $299 and XB1 S at $249. 

Its at 29.9m atm (front page), and probably a tiny bit overtracked.

Reguardless.... yes Xbox One will probably go over 50m.

No. Won't hit 45 million either.

Depends on how long Microsoft plans to keep it on the market, and with how many revisions. I doubt it's as high as VGC has it in the first place, and it's safe to say I'm not a believer in 50m.