I think the supermakets are more used to changing times than you realise. Before the pandemic they had teams of people studying the weather forecast to anticipate the demands for summer BBQ food, only to switch at the last minute to a wet weather plan.
They have kept up with people panic buying this year, and the changing trends with more people being at home, and now they have Brexit to contend with. I think they have a better handle on what we're all going to buy next week, next month than we have ourselves!