"On August 21, 2013, we are ending the current NFC redemption of gift and loyalty cards added to Google Wallet," the email says.
"If you've already redeemed your gift cards, you don't have to do anything. If you have a balance remaining and you'd like to spend it using the tap and pay functionality, you must do so by August 21st. If you still have the physical gift cards, they will continue to work even after August 21st."
Support for NFC credit and debit cards will continue as normal, the email adds, and "we're working with retailers on other options for gift and loyalty card redemption within Google Wallet."