This is a complicated situation. Many of us hoped that as an EE, David could come in and compete for the starting job. However, prior to the injury I think there were signs that developmentally (like virtually any QB his age), he wasn't going to be ready to start as a true freshman.
Also, there are signs that Alabama's top QB from the previous class (Bateman) isn't going to be ready to vie for the starting job either. This complicates things, as Alabama would hope to have one of their elite QB prospects in a position to compete for playing time.
But, what does Alabama gain by greyshirting Cornwell? They insure that no QB from this class will be available the following season? They put Ricky Town in a class with another QB?
I have to assume that Alabama will give Cornwell a scholarship, as planned (EE, no greyshirt), and if anything they might look at JC guys, or you could see someone like Coker transfer in. But, I just don't see an advantage to messing with Cornwell's offer, he's got too much potential, and Ricky has too much potential, to really mess with the situation too much.