Why future tense? “This is the last time he’s going to stand me up” [closed]

Why does the second part of the phrase use future tense? Although the event “the last time” is happening now, we refer to it using future tense. It also works with “will:”

“This is the last time he will stand me up.”

Any ideas?

In this sentence, it is stated that in the future he will not perform the action of "stand me up", even though the sentence is being said in the present. The sentence is informing about the action which might/might not happen in the future. That is the reason why it is written in the future format.

"This is the last time he will/is going to stand me up.” is a prediction.

Let us assume that he has stood the girl up three times:

The first time that he stood the girl up was not the last time.'

The second time was not the last time.

The girl is saying that this time, i.e. the third time is going to be/will be the last time, because there is going to be/will be no fourth time when he will stand her up.