Future perfect continuous
will/shall + have + been + verb + -ing
Future perfect continuous or the future perfect progressive is used to talk about an action that will continue to happen up until a specified time in the future. The action that occurs must stop before another action in the future using a reference to time.
I will have been living in London for two years by next December.
She will have been studying Spanish for an entire year when her new former teacher comes back.
They will have been working for the company for nearly ten years when the layoff occurs.
Those students shall have been chatting for the entire lesson by the time they finish.
We use the future perfect continuous to demonstrate the cause and effect of an action before another related action in the future further ahead.
George will be exhausted when he gets home because he will have been working all day.
Isabel’s English will have improved so much when she returns from England because she will have been living there for three years.
The car will be all dusty when we get it as it will have been sitting in the garage for six months.
The future perfect continuous can also be substituted with the ‘ be + going + to + have + verb + ing’, which is completely interchangeable with the standard form. ‘Am/is/are + going + to + have + verb + verb + -ing’
She is going to have been working on that project for over five hours by the time we get back.
They are going to have been playing football all day by the time they finish.
Henry will be furious when he gets back because his children will have been arguing amongst themselves.