See above."I have been married 27 years next month. About 2 months ago my husband
tellstold me he doesn'tdidn't want to be married any longer."
(Note: the use of the present tense is possible in this context but it has a very specific use which I personally wouldn't encourage learners to use.)
1)Would this be a colloquial use for "will have been...."? Yes.
Would there be much difference in conversation between "I have been married 27 years next month." and "I'll be married 27 years next month."? I wouldn't say the latter. I would say it's between "I've been married 27 years next month" and "I'll have been married 27 years next month".
2) If I didn't know how long they have been married for next month, would it be acceptable to say "They may have been married 25-30 years next month."?
That sounds unnatural. I would use "Next month, they'll have been married somewhere between 25 and 30 years, I think."
- For Teachers