Learn English – “I wish we don’t do that again in the future” or “I wish we would not do that in the future”

Since English doesn't have a future tense, somebody has to do it.

Will and shall are auxillary verbs that are used, among other things, to refer to future time. They attach to the noun as 'll.

Regarding your questions:

It is grammatical.

It is covered in textbooks (example).

Yes, you can say:

Then you call me and tell me where you are and I'll join you.

Strictly speaking I'll join you is not using a future tense.

These distinctions are simply guidelines but not hard-and-fast rules. The shift of tense does not indicate that the event has not taken place.

Let's say that she agreed last week to have lunch with Susan today, to discuss a business proposition. The lunch does take place. She has a sandwich. Susan has soup. If the question is about what she said, it doesn't matter whether the lunch took place or not:

When I spoke with her on the phone, she said she would have lunch with Susan today, and they did indeed have lunch. She's a woman of her word.

Not needing to change the tense when the assertion is still true does not imply the corollary that changing the tense means the assertion is now false:

He said his brother worked in Milan.

His brother may still work in Milan. The shift of tense signals that the speaker is reporting the speech of another, not making the assertion himself.