I'd say it's rather unlikely the game will work unofficially on older versions of Windows, because it will most likely use the DirectX 12 API which is only available for Windows 10. They would have to also support DirectX 11 in order for the game to run on older versions of Windows. And that's just the graphics API. If they are advertising it as Windows 10 only, they most likely wouldn't have wasted all the effort required to add in API support for older operating systems at all, meaning it wont be able to run at all on older operating systems.

In order for any game coming out to run on older versions of Windows, they either have to use both new and old APIs, or just limit themselves to older APIs like DirectX 11 and give up on new features and performance of the new APIs. For a game like this which is so cutting edge, they're guaranteed going to be taking advantage of current generation graphics and other APIs though.

The only likelihood of it running on older Windows releases would IMHO be if they built the game engine on top of the Vulkan API. Personally I think that would be the best choice as it would provide all of the same benefits that DX12 provides more or less, but give the option for the game to be easily ported to older OS releases if desired, as well as to other platforms like Mac, Linux etc. The previous version of the engine was built on DX though so I presume they're building the new engine on that as well.

But the graphics API being used is not the only API to target, audio and various other things matter as well as any middleware they are using and whether the companies that provide that middleware plan to support it long after support for EOL versions of Windows dies.

Economically it makes no sense to support EOL versions of Windows due to the overhead of maintaining it and things breaking. It gives customers false hope, which is why very few companies bother to do it.

People should set their expectations about what the game will run on directly to match what the company is stating clearly the game will run on, which is Windows 10. I would not expect it to run or be able to be made to run on anything else honestly. They'd have to take too many concrete decisions to add code to the game to make it run on older versions of Windows. It's not impossible and tonnes of games on the market now do just that by providing DX12 and DX11 support built in, as well as any other multiple APIs needed under the hood. But they only do so because there is a large enough market out there using these operating systems and the systems are still officially supported by the OS vendor.

In the case of Cyberpunk 2077 however, it releases *after* Windows 7 goes EOL, and the number of people still using Windows 7 at that point in time will be much smaller than it even is now which is shrinking every month.

So it'll be an unpopular thing to say for many people's eyes to read or ears to hear, but I'll go on record to predict that the game will not run on anything older than Windows 10, and I don't expect that to change officially nor for it to be able to run unofficially on anything older.

For the record, I use Windows 7 and would love nothing more than to hear Microsoft is going to extend it's life officially by 5 more years. I hate Windows 10 and do not want to use it, but I know I'm going to be more or less forced to use it one way or another whether I like it or not (and my laptop already has it so I already bit part of that bullet and don't care for it). So I'm not a fan of this stuff happening, but I observe it and recognize it for the reality that it is ultimately no matter how bad it tastes to say it or hear it.

I will say that I will be pleasantly very pleased if they have chosen to use the Vulkan API for CP2077 however, and such a choice would make it at least viable for them to make the game available for other platforms in the future if they thought there was enough market interest. If it's DX12 based though then that's very unlikely to ever happen.