I've heard that a different design of heat shield will be in place for the future Orion missions. How is the heat shield going to be different, and will the (Planned) Dec 4th launch of Orion adequately test the proposed changes to the heat shield?
My read of this article is that the material is the same, but rather than filling small cells in-place, they'll be building larger blocks separately and putting them together. So this upcoming flight test should still be a valid test of the material's ablation rate, as well as the other aspects of re-entry that aren't directly related to the heat shield.
(Personally, I'd rather risk a finger-sized cell with less ablative fill than it's supposed to have, rather than have an entire block of heat shield fall off a la Columbia, but I will assume the Real Rocket Scientists are on top of it.)