If you use Google specific functionality, then yes,you have reasons to worry. If you are host agnostic and use Google cloud just as a deployment target, then you shouldn't worry.
Sunsetting GCP will immensely damage their reputation.
However, they will absolutely shutdown some of the other value-add services like AI-as-a-service and some of these others that are probably not being heavily used.
They need to be competitive, and to do so, they must be at least feature pairing with AWS/Azure. I can't think of a single service they can simply shutdown. Actually they need to build more.
I am an AWS long time user. I have toyed around with GCP, and I found it a very disconnected platform. They don't seem to have a unified story around it.
AWS is not perfect, but it is just waaaay ahead. You can tell, they are a heavy customer centric company.
While I'm usually nervous about Google discontinuing things, they'd be idiots to cancel something with $6B in revenue growing that fast.