At least, that's the word from a tipster to Eater SF:
A tipster spotted a sign in the window of Duc Loi Supermarket (2200 Mission) advertising the arrival of “duc loi kitchen coming 3/15 - 11am-7pm” with “sandwiches.” “Authentic Vietnamese” options will be offered among other things.
I would head over there right now to corroborate the story and gather some additional details (like, for example, will they have bánh mì and will it be delicious?), but it's raining outside and that's hella cramping my style. So in the meantime, let's just speculate as to what the level of deliciousness this might be and hope La Niña gets bored and stops sending us rain by Thursday.