I could not generate a SKU automatically with this module since none of the tokens are unique except the title of the product. I tried [nid] token but this does not work since it is null because the node has not been created yet in presave state.

I looked at the Auto SKU module (http://www.ubercart.org/contrib/4307) and decided to merge the auto sku functionality into this patch.

So now you can:
1) use [nid] token in pattern.
2) if pattern is empty it will automatically generate the sku by using $node->type . $node->nid
3) you can use PHP code to generate the pattern if the user permission is enabled to allow php code