1. You can always export your stack's state a. You can move to managing your own state locally or in a bucket, for example. The only caveat is that you aren't taking advantage of Pulumi Service only features, such as the fully qualified stack names

<org>/<project>/<stack>

2. Your infrastructure is deployed, you'd don't lose it if you stop using Pulumi

If you're talking about the Cloud API that abstracts cloud providers, you're kind of locked in, but you can still do #2 from above.