I went with "Maybe" option as I still think that it will take way too much to really even come close to 360 numbers.
First of all, back then Sony literally handled a ton of advantage to Microsoft on their own. A lot of things were in favour of 360 - early launch, better pricing, better and easier to work on hardware, which also led to some developers working exclusively on 360 games at the time. There wasn't that much of negative legacy from Xbox generation either.
Second, as can be seen based on charts here, 360 surely started to decline already back in 2009 after it passed 40m mark. Kinect did a lot to boost sales further. If it wasn't for Kinect, I think 360 sales could have easily been at least 15m less than what we have now.
So, despite the fact that this is probably gonna be the gen where Xbox should theoretically have the best first party software lineup in it's history, I still think that Xbox Series will end up selling a decent amount less than 360 did. No huge advantage over PS5, still remaining negativity from Xbox One generation, games releasing also on PC, no Kinect-like miracle which will add 15m sales out of nowhere - all these facts go against such possibility to match 360 sales. But who knows?
I think we can expect LT sales around 60-70m at this point if Microsoft plays their cards right. And if they don't lose their way due to euphoria from such success, then maybe the gen after that would be the one where they can try to outdo 360.
P.S. I think some people in gaming community really overestimate the importance of ActiBlizz acquisition effect on console sales. The deal will be finalised only by mid-2023. And we probably won't see any exclusive content until late 2024, because they simply won't cancel games already in development for Playstation consoles. By late 2024, the gen will be practically done and most likely both PS5 and Xbox Series will pass their peaks anyway.
