I a shop with 10 products, yes, I'd agree. In a supermarket with thousands of products, they can predict what you're likely to buy if you're a regular customer and you might be the only one buying those items that day.
I don't expect them to do it overnight. First they roll them out for the cost savings. Just like they did with barcodes rather than price labels. Then they start to look at other savings or profit centres.
After a while it becomes, why wouldn't they do it?