Concerning whether the data classes should be designated as mutable or immutable, work is still in progress. Both options have advantages and disadvantages. Immutable data works well in multithreaded, parallel, or concurrent systems. On the other hand, mutable data works well with cases that require frequent modifications to data.
Concerning thread safety, since the data classes are not yet designated to be immutable, it is the responsibility of the developers to use them in thread-safe configurations.