Now that WFH has been "discovered" it's doubtful. I mean if everyone works from home just one day a week, that's 20% fewer sandwiches they will need to buy.I’m not so sure. Just because you’re working from home, that doesn’t mean you want to spend a significant amount of time shopping for and preparing lots of different things for your lunches. If you were OK with that, you could easily have taken a packed lunch to work before and probably saved quite a bit of money, but the existence of the sandwich shop as a concept suggests that plenty of people prefer the convenience and variety they offer.
What I do expect to see now is a rebalancing of where these places are found. Not so long ago, we moved from a busy area of Cambridge (UK) to a village a few miles outside the city. Life is different here, but better in most ways. We don’t have a Pret sandwich place or a Wetherspoons pub here. We do have a couple of local cafés and a baker, though, and several other pubs. We also get something I had only noticed in passing while living in the city, which is the food trucks that travel around and set up in a different spot each evening. Each truck typically has its own speciality cuisine and they’re great if you want something interesting for dinner.
As far as I can tell, these are all independent small businesses, often run by the owners. We were worried for them during the months when almost everything was closed down because of the virus, but fortunately they made it through and now they seem to be thriving, presumably because they’re well placed to serve a suddenly-larger local market.
I have nothing against Pret. I've eaten there many times when I’ve been travelling for work or shopping for a while in a big place. But almost everything is better about those local businesses I mentioned. If the strange circumstances this year cause a permanent change in our lifestyles and if that makes local catering more viable at the expense of the big convenience chains aimed at a commuting workforce, I find it hard to see a downside, at least in the long term after a possibly disruptive period of change. The trade and jobs will probably still be there, just in smaller businesses serving their own communities.