Hi,
Here's a line from Friends:
I am never having sex with you again!
(Sorry for the terms, but that's what the character said)
Shouldn't it be will? Isn't there a rule for will that says it is used for promises, refusals and threats?
And isn't present progressive/continuous only used for arrangements?
The person could certainly say 'I will never have sex with you again'.
The use of the Present Continuos is also OK. It suggests here, as you note, that the two people have an arrangement about having sex regularly.
Clive