AMEX winning the co-brand battle doesn't mean the SPG card won't see severe devaluation in the future. I guess it's good that AMEX won't lose a decent chunk of their customers.
Chenault is also not a winner... He's an embarrassment to the company. American Express has fallen a million miles under his watch... Everything to benefits, rewards, and customer service plus everything in between has either been matched or surpassed by other issuers, despite the fact that they're a closed loop network that doesn't have to share their higher than average interchange fees with banks, not to mention the major loss of a few co-brand partners. Buffett should've ran Chenault out 10 years ago. Marriott probably decided to keep AMEX as a co-brand partner because they know Chenault won't be there in the spring.