We must also not forget that other companies have since proven that the idea of a proprietary operating system (or just kernel) as the main base of IP has started to look somewhat obsolete anyway. Now we have proprietary services and systems like Android and macOS have demonstrated that you can take an (at least partly) open source OS and slap most of the proprietary bits in userspace quite successfully. For that matter the "next version" of Windows might as well be a rebranded version of Android or something. Why keep maintaining your own OS kernel when you can have the community do it for you with a modest donation?

NT will be with us for a while yet, though I can't understand the business case for not end of lifing it at some point, especially when most of the engineers you hire don't know it well.