Shall or Will?

The rule used to be that, for the future tense, you used “will” in the first person and “shall” for second and third person. I will jump, you shall jump, etc.

This rule went away and now we use “will” for everyone. I think it happened about the time I was in sixth grade. I remember “shall” being taught then, but heard only “will” when I got to high school.

For what it’s worth, I remember Gen. MacArthur’s “I shall return” after retreating from Corregidor in World War II being discussed as technically incorrect, and that his intent was to express emphasis.”

So here:

So is she right or wrong? Maybe okay if she wants emphasis.

Somewhat off topic: The Army style guide says to use “shall” as an imperative. Something like “You shall open the valve slowly.”