What happens if the employer cancels the spouse's I-140 after the transfer.
If the H4 is transferred 'properly' before the I-140 is cancelled, you should be able to keep your H4 EAD until the end date on the card. However, if the I-140 is cancelled prior to the transfer of the H4 status to the new H1 or it is cancelled during the transfer, there is a chance that your EAD will be revoked.
We recommend you talk to an experience H4 visa lawyer or EAD lawyer before you transfer your H1B or H4. Shah Peerally has fought for years for the rights of the H4 and ultimately the H4 EAD. He is a very experienced immigration lawyer, please call him at (510) 742 5887 for a full consultation.