Stable Structures: Removing the Bounded Size Requirement

I can’t find a straightforward/updated answer to this. Do we know how builders should think about storage capacity when deciding to use stable structures in production?

For example, what if an app (e.g. taggr/hotornot) reaches the canister limit on the Stable bTreeMap that stores user posts (4GiB?). Can it be migrated/copied to a multi-canister architecture while preserving the origingal bTree? What’s the upper limit on storage like this?

And thank you. If it wasn’t for this library I couldn’t build anything here.