People used to ask us when we started Userify (SSH Key management, https://userify.com)... what happens when AWS clones you?
Well.. that was five years ago, and they haven't cloned us yet. But even if they ever did, they have a vested interest in ensuring lock-in to AWS, so they will always choose to make things work with things that only they offer (such as IAM) instead of making it cross-cloud. That makes things a lot more challenging for large enterprises, especially when you're talking about users that may have to log in to servers hosted in multiple clouds. Having multiple sources of truth doesn't work at scale.
Most large organizations are at least on AWS, GCP, and/or Azure already, so I don't really think Userify's SSH key management (or any other cross-cloud tools like ansible/pupet/terraform/etc) are going away anytime soon.