Yes. They're not in any danger of disappearing. They just don't have any purpose anymore. They don't provide anything to the market that can't be gotten elsewhere, more cheaply, at higher quality, with better support, or with any other product advantage you might suggest.
The only advantage they have is inertia; software works on windows that doesn't work on other platforms. Those are a tiny, tiny percentage of cases. Microsoft brings nothing to the table; you're going to have an easier time, be more secure, spend less money, deal with less hassle, if you use Linux. Linux hassles me less over the course of a month than Windows does in a single day of use.
So yeah, Microsoft has a lot of wealth and resources. They don't have a point, anymore. There's no innovation, progress in development, novel or unique products, etc - they're effectively dead, as far as the market goes. They're going to have to undergo an epic struggle and battle for relevance, or within 20 years they're going to be a lot like IBM or Yahoo or even Bear Sterns.
They're the 4th largest company because they underwent an epic struggle and seized on a purpose and were driven to develop the best in class enterprise operating system and went tooth and nail against Apple for decades. Now they're a second rate mishmash of adtech surveillance grifting, meaningless, flailing product development, prancing around and cashing out the reputation that was built, and supremely vulnerable.
But yeah, they're big. I'm sure that will suffice to keep them alive for a long time. There just won't be a point - unless they get leadership that revitalizes the entire organization. I don't see that happening.