Chili's is already starting down this path. At the location near me you can order drinks and pay through a device at the table. They haven't jumped in all the way as food orders are still through a server.

Though, as someone who has had a credit card stolen via gas pump several times, I'm really hesitant to use a card at one of these devices. They're probably not very secure to begin with and then you couple that with the fact that anyone can sit with one of them for an hour or so with no scrutiny, it's just ripe for exploit.