Disclaimer: I work at Google Cloud on GKE/Kubernetes.
My personal opinion is that, how closely you're integrating with storage systems (e.g. databases and blob stores) and APIs (e.g. machine learning, pub/sub, load balancing) of the cloud platform you are running on.
Kubernetes already does a great job abstracting the compute infrastructure and networking topology you have on the cloud provider away. There's a lot of work going on in the Kubernetes Service Catalog[1] to make it even more platform-agnostic. With Service Catalog, you will be able to say "I want a Redis instance" and your underlying infrastructure will be able to provide you a Redis instance, you will no longer worry about integrating to GCP, Azure, AWS separately. Service Catalog sounds a lot promising as a step towards eliminating vendor lock-in. That said, it is still a work-in-progress.
Note that none of this offer a migration path for your existing databases etc. But I am seeing that many businesses are able to migrate their compute workloads between platforms and on-prem to the cloud a lot easier compared to the pre-Kubernetes era.
[1] https://github.com/kubernetes-incubator/service-catalog