There are a few points that makes me think that Series will outsell One:

- Series X had a better launch than One.

- Microsoft bought Bethesda and other studios.

- Gamepass is getting a lot of attention.

- Series S is a cheap alternative to next-gen games.

My guess is a healthy 80-90 mil. I see things going much better for MS this gen, and they are making a lot of smart decisions. They are also in a position to deliver on some very good console exclusives to bolster the gamepass library, all they have to do os deliver. The ball is in their court in terms of being able to expand their audience back to 360 levela, and I think they just might pull it off. Only time will tell.

If there were a 75-85 million that would be my guess.

While the One faced a confusing launch, $100 price premium over its more powerful competitor and a chronic lack of first party investment early on, the Series X is the better hardware, in position on price (and with a Series S) with a lot of value in gamepass and a lot of 1st party investment. 

Also exists within the context of an ever-growing console market. Even if it didn't grow in market share compared to Xbox One, it would still outsell it by 5-10m purely on the trend growth of the market.

Why would they stop supporting Series S? They likely already sold millions of it and it leads to them having the cheapest 'next gen' console on the market which makes it an enticing option for parents, people who mostly play the yearly FIFA/Madden/COD and everyone with a tight budget. Also there is practically no technical reason to not continue scaling down the resolution down a bit and simply releasing the game on Series S.

You yourself said that Series X should sell well once first party output starts. Xbox One never sold well and still managed to sell 50 million consoles. In general I don't get how it should manage to sell less than One except if the console space starts to shrink in the near future in general. And nobody is predicting that right now. 

This one is tougher than PS5 one. For PS5 the 100-125m option perfectly matches with "around PS4 numbers". Here "around Xbox One numbers" can either be 25-50 or 50-75. I initially predicted 40m for Series X|S for the same reason as mentioned in PS5 thread, but seeing initial sales I think II might risk and up prediction for 50-75 range. Will strongly depend on Microsoft's first party and their overall strategy, but if I were to guess it can end generation anywhere between 40 and 70m. Most likely ~60m. Would be pleasant to see Xbox return to 360 levels as some here predict, but it's really hard to see how it can be possible. Xbox One gen just did too much damage to the brand's reputation that the whole Xbox Series gen will be spent by Microsoft to regain the mass market consumer trust.

A lot will depend on how strong its first party lineup will be, which is very much an unknown at the moment. They may have a lot of studios but whether that leads to a lot of system selling software is another matter entirely. Whether they get Halo back on track or not is another variable as a return to form there could move a lot of consoles.

30M-40M

I just really think a gaming console lives and dies with the games exclusive to it. Right now there is zero reason to go and buy an xbox. This higher sales over the x1 as we are seeing is no more than the fan base that was gona buy it no matter what. It should eventually reach its cap. If all of these studios dont have anything to bring in new gamers before then we will see a very steep decline.

I completly understend the current situation the xbox is in and how all theese purchases will produce games later on, but if they wait to long the lead the ps5 will have will be to much. A snowball effect will happen than will impead the xbox to close the gap no matter how good the eventual line up gets.

I also dont think their line up is going to improve that much. Just look at halo infinite. That game was laughed into rework for a full year but the execs at MS thought they had hit with what they showed. I think that shows the kind of quality they are planning on filling gamepass with.

Series S is a joke to be honest. around the world is readily available. Its a console that will become irrelevant no later than next year. specially with the release of xcloud. Whatever demographic the series s was supposed to satisfy xcloud will do so as well.

and finally yes the series is in a stronger position than the x1, no doubt but the series is not competing against the ps4. its against the ps5 and the ps5 is also in a much better position than the ps4. Just this very first year the ps5 has already released more big hitters than what the xbox has planed for the year and we still got big ones like ratchet and clank and horizon to wait for. Halo alone will not win over gamers. all those studios starting to bring out games maybe late 2022 is probably just a bit to late. the ps5 could have a 20m or more lead that will just keep growing.

30-40 seems way to low. I think anywhere betwen 60 and 90.

While Game Pass is an excellent offering and giving MS highly positive word of mouth right now, the real sales driver is exclusive games and with Bethesda under their belt aswell as other acquisitions finally coming to fruition I think MS could have enough power there to sell 100+m this gen.
Sure, all of those games also come to PC, yet as someone who played on PC exclusively for almost a decade I think it's great to just buy the console and know it'll get a more than adequate version (maybe missing some bells and whistles) tailor made for it.