三人行，必有我师(焉)

For me 会="will" does sort of intuitively work as a present-habitual thing if I think of the structure like an if-then clause -- like, "if X happens, Y will happen," except that instead of "if," it's "whenever / every time / when."
Oh that makes a lot of sense, a good way to put it.
I think it was tinny who said a while back that she thinks of 就 as like an arrow pointing to the thing that comes after it, and 会 here is a bit similar!