The extension ID is derived from a private key that the developer uploads with the first upload to the app store, and the ID will change if any subsequent uploads include a different key.pem in their zip file (but if there is no key.pem then the extension ID will remain the same).
Therefore, if the extension ID changes, it's possible the owner changed. However, it's also of course possible (and even likely) that the original owner might transfer the private key to the new owner. And since Google doesn't require each upload include the private key, then the new owner could push changes without even needing access to that key.
I find the extension ecosystem fascinating and I'm also working on some tools for this space ([0]: warning, WIP hobby code). For example, I want to create a GitHub repo that targets a specific extension, tracks its updates, and pushes each one as a change to the repo. And then I can run static analyzers on the code after each update, and also some runtime taint analysis I've been experimenting with (e.g. tracing user inputs into dangerous sinks like eval or postMessage).
[0] https://github.com/milesrichardson/crxmon
Therefore, if the extension ID changes, it's possible the owner changed. However, it's also of course possible (and even likely) that the original owner might transfer the private key to the new owner. And since Google doesn't require each upload include the private key, then the new owner could push changes without even needing access to that key.
I find the extension ecosystem fascinating and I'm also working on some tools for this space ([0]: warning, WIP hobby code). For example, I want to create a GitHub repo that targets a specific extension, tracks its updates, and pushes each one as a change to the repo. And then I can run static analyzers on the code after each update, and also some runtime taint analysis I've been experimenting with (e.g. tracing user inputs into dangerous sinks like eval or postMessage).
[0] https://github.com/milesrichardson/crxmon