I don't think you'll see very many bars immediately going out and start cracking big bottles. They've got an inventory of little bottles they've got to get rid of first, and the only way they can get rid of them is to sell them.
This was not really unique in the 1970s. Over the years, as moderation became the big thing, the little bottles fell out of favor.
The bar or restaurant has their choice of whatever size bottle they deem best for the business or their customers. They might go with minis totally, or they might go with big bottles totally, or a combination of both.