As Kotaku reported last week, GameStop will indeed be selling Steam codes, the retailer said in a press release today.
The program is called Steam Wallet and codes will be available at $20 or $50. You'll be able to use them to access Steam's "more than 1,800 titles," GameStop said. You can buy them in some 4,400 of GameStop's stores starting today.
"We are thrilled to be partnering with Valve on this new initiative," GameStop's Steve Nix said in a press release. "This gives even more options to customers now that they can put money in their Steam Wallet using cash, gift cards or trade credits through our convenient neighborhood locations."