Orleans 4.0 GrainId and StreamId forward compatibility

Hello,

The breaking changes section of the release notes of the 4.0-preview1 reads:

> Since GrainId and StreamId are so different, persistence, streams, and reminders are not forward-compatible yet.

Is this situation only due to preview 1 not being feature complete yet or does this mean that we will have to migrate persistence, streams and reminders manually when migrating to 4.0? (which sounds like a huge hassle).

We are not in production yet with Orleans so knowing if there is commitment for backward compatibility for these features will help us determine if we can continue to "blindly" rely on them by treating them as stable 1st class .NET framework components, or if we are expected to add abstraction layers to plan for migrations due to breaking changes across major versions (if the official position is that we should not expect these features to be backward compatible).