They won't let you run out of food supplies because that would just end the game. If you do somehow, there will have to be a merchant somewhere who sells more. And then running to that merchant will just be another trivial chore.
I didn't mean that the game would run out of food that you could eat, but the fact that you will have to leave some areas and go to town to buy supplies if you want to use long rest too often. That's why I said "soft lock". And I definitely think there will be dungeons and areas in the game that you won't be able to leave to replenish your food supply. In that case, you'll have to think carefully about each long rest, because you don't know how many tough fights await you before you get the chance to buy more food.
