The old saying that no one ever got fired for choosing IBM could be applied equally to AWS. The companies that chose IBM in the 70s and 80s can still buy new compatible systems. The companies that chose Stratus or VAX, not so much.
I think you're committing something of a "fallacy of the excluded middle" here. Those aren't the only two things that can happen. AWS could, for example, continue offering the service but not to you. We've already heard stories of AWS accounts being closed for various reasons, and it's hardly a stretch to imagine a CloudFront / Daily Stormer kind of scenario where Amazon decides to punt you for taking an unpopular political position, etc.
I would even say that your company going out of business is a bigger risk than depending on AWS.
I would say that I disagree, in at least some cases.
Even businesses that chose Microsoft technology in the 90s when they were the clear leader have had a relatively painless upgrade and support path. They abandoned VB6 15 years ago, but you can still wrap your VB6 code as a COM object and interact with C#.
I’m saying that it is the safer bet to go with the largest provider with the largest customer base. In the 80s that would be IBM, in the 90s, MS over SUN (and the royal claustrof%%% that Java has become under Oracle) or Borland.
Let's look at yesterday's equivalent to AWS- Sun Grid. Sun was viewed back during the first dotcom era in much the same way that AWS is today. All that it would take to completely bork it would be an economic catastrophe that mirrors the first dotcom bubble. Obviously, Sun Grid is no more.
[1] https://news.netcraft.com/archives/2004/11/16/solaris_remain...
You can still buy Solaris based systems today but you would have plenty of time to migrate. But seeing the writing on the wall you would have plenty of time to migrate.
There's more to building a long-term, sustainable business than optimizing revenue at any cost. And part of that "more" is exactly the work you to do insure against future risks.