If they could (quickly) come out with a personal assistant which was really useful for people's planning and shopping and productivity, which knew how to navigate the apps and services on a person's apples phone/computer/cloud data, and do it locally and/or privately... They'd be in a good position even if it wasn't the absolute leader of the pack.
AI is going to be so powerful in the coming years that if apple falls behind AND doesn't give the keys to some other company to integrate AI, then I could see people jumping ship.