var editPost = wp.data.select( 'core/edit-post' ), lastIsSaving = false;

wp.data.subscribe( function() {
        var isSaving = editPost.isSavingMetaBoxes();
        if ( isSaving !== lastIsSaving && !isSaving ) {
                lastIsSaving = isSaving;

                // TODO: ajax call to get metabox HTML

                // TODO: refresh the metabox container

                // TODO: ajax call to get the notices array

                // TODO: submit notices to Gutenberg for display

        }
        lastIsSaving = isSaving;
} );