It validates Phase 3 as a product. Core Power and Phase 3 are both milk-based recovery drinks, though Core Power seems to target more the endurance athlete crowd, while Phase 3 seems to target more the extreme sports and jock-type sports crowd.
The fact that Core Power was picked up by Coke means that Coke thinks it's a viable product with a growing market.
Sure, it's disappointing that Phase 3 wasn't picked up by Coke, but that doesn't mean it won't ever be picked up by coke or some other large beverage company. Who knows, Core Power may take away muscle milk profits and prompt Pepsi to pick up Phase 3, which is a much more similar product.