I don't know this for sure, but I would expect that it will be a long time if ever.

If the Father was my client, I would probably advise them to mail in the return...or if they have a refund without the dependent, efile then amend.

Or even work out a cash transfer between the two of them and not amend either return, if the benefits are close to the same for each of them.

Of course stimulus credits etc. may mess up that idea.