I think that's the impression you get if you focus on Microsoft as a OS vendor. It's not that anymore, that's why their OS sucks for many years now. Their main business is b2b, cloud services, and azure. I think they are pretty safe from OpenAI. Plus they have invested big in OpenAI as well.
Windows is hard to replace in large organizations. Is there actually any real AI competitors in the stack? Well Google, maybe. The whole Windows+Office+AD+Exchange and now Azure stack is unlikely to go any time soon. However badly they screw it up.
True. Basically any medium to large scale business is reliant on Windows/Office/AD. While there are open source alternatives to Windows/Office, I can't think of a good open source alternative to AD/Group Policy/etc
