Don’t be so silly, they will lose far more active customers if they’re not evolving the product. Plus they will fail to attract new customers. You won’t suddenly lose the ability to run Cubase 10.0.x and it won’t deteriorate in any way.
If you’re happy to stick with a 10 year old OS, then why is it so hard to use a 1-2 year old DAW once C10.5 and C11 comes out? You either want progression or not, and no-one is being forced to upgrade - if you want to stick with what you have, then do so. If you want improvements then upgrade, it’s a very simple logic, and takes a matter of hours. You’re months away from running an insecure/exploitable OS which will start to lose online services radically - which isn’t great if you’re running a cloud service for archive/backup or frequently going online with it.
Actually, you probably aren’t using online/cloud as you’ve mentioned fear of being spied on.
If you’re scared of Win 10 and Cortana, then best cut your bank and store cards up, wear a bag on your head when you’re walking or driving, blank your numberplate, throw your phone off a cliff, cancel your internet and cover your house in a foil dome to prevent any hardware directly seeking a wifi/4g signal to track activity.