From a business standpoint, I seriously doubt that Domino's is targeting those with celiac disease, considering that less than 1% of the US population has it. Hardly a profitable demographic. As David mentioned, GF is a current dietary fad.
There is a restaurant near me that is owned by a guy who has celiac disease. He has monthly gluten-free buffets that are by invitation only for his celiac friends. He actually built a separate kitchen for preparing the GF fare. People come from many miles away. There wouldn't be nearly enough celiac sufferers in a Domino's delivery area.