Cannot use referencing node tokens in SKU

The thing that is confusing me about your reply is that Commerce core uses the title field of the display node to create the title of the product when automatic title generation is enabled. So, it seems to me, at some point during the creation of the product the referencing product display node is available.

I see what you are saying about multiple displays for products but when creating product variations in the display node editor, perhaps you can get this information. The inline entity form module code which does this is as follows:

 // Generate the product title. Take the parent entity title as the base.
    if ($this->settings['autogenerate_title']) {
      $entity->title = entity_label($context['parent_entity_type'], $context['parent_entity']);
      $attributes = $this->attributes($entity->type);
      if (!empty($attributes)) {
        $wrapper = entity_metadata_wrapper('commerce_product', $entity);
        $attribute_values = array();
        foreach ($attributes as $field_name => $attribute) {
          $attribute_label = $wrapper->{$field_name}->label();
          if (!empty($attribute_label)) {
            $attribute_values[] = $attribute_label;
          }
        }

        if (!empty($attribute_values)) {
          $entity->title .= ' (' . implode(', ', $attribute_values) . ')';
        }
      }

Any comment will be greatly appreciated.

I would use this because my SKUs are generated based upon a value in the product display node, the SKU_Prefix.

All product variations have SKU components that I would like to get from the referenced taxonomy and the variation itself.

So, all product variations for a specific node would have a SKU like so,

SKU_Prefix - Variation Component - Taxonomy 1 SKU Component - Taxonomy 2 SKU Component.

For example, a product variation which is for the display node, Basket, with a Finish of Brushed Nickel, and an Installation type of Stone would have the SKU

T100-001-BN-S

Hopefully this clarifies my specific use case.