Sure. It’s just much easier to tell that Windows 7 does not support HiDPI (or that W7/W10 support for HiDPI is “totally different”) to a non-programmer than to someone like me who has some understanding and experience in programming C++/WinAPI DPI-aware applications with Windows 7 support.
I’m not sure what you mean.
There is probably a wrong assumption here. For example, my PC is from 2011, and its performance is still quite enough today even for 4K.
Hardware upgrades are often partial: e.g. I replaced my original i3-2100T CPU to i7-3770T with the same socket and no need for changing anything else including Windows version; I replaced my graphics card to GTX 650 Ti Boost in ~2013. Then bought a 4K monitor in 2015, and my graphics card already had the DisplayPort port required for 4K@60Hz.
None of those partial hardware upgrades forced me to change my Windows version. This is not a niche situation, this is a regular situation corresponding to the nature of the open PC architecture available since IBM-compatible PCs appeared.
The only issue with HiDPI in Windows 7 that could be called serious was that Windows Explorer had unusable proportions of address bar and search box at Windows zooms more than 188% (I use my 4K monitor at 200%). But I successfully overcame the issue with the ExplorerHiDpiFix utility developed by myself.
Focusing an application development solely on new users and ignoring interests of existing users may be something relatively appropriate with other types of software, but this is probably not reasonable in long term as for professional musical software. Unfortunately, Steinberg already did this when removed the Cubase-VST-project-import feature from Cubase (SX) 4+ (though long-term Cubase users have tons of old projects), and continued to go the same way when stopped supporting 32-bit systems in Cubase 9+ (though musicians have tons of projects that use old discontined 32-bit-only VST plugins).
But the crucial detail with HiDPI support in Cubase 10 under Windows 7 is that Windows 7 itself is still supported, it’s just HiDPI support that is missing in Cubase 10 under Windows 7. And as long as HiDPI support is implemented properly, it is unreasonable to support HiDPI under Windows 10 and not support it under Windows 7 at the same time.
Windows 7 won’t magically stop working once its support is ended. Support just means security updates, but those updates are not necessary for Windows itself to function in the first place. Moreover, many professional musical computers are not even connected to Internet, so there is no risk for them in not getting updates, and many musicians don’t even care. So Windows 7 will most likely keep being used and popular far longer than until 2020.
Even Windows XP is still used, and some big russian software developer — 1C — has even recently created (article in Russian) a custom version of the WebKit engine (built into their software) to prevent losing Windows XP users. There are software developers that set a high value on their long-term users.