Future Perfect Continuous

The Future Perfect Continuous tense looks at the past from the future.

How do we make the Future Perfect Continuous Tense?

The structure of the Future Perfect Continuous tense is:

subject	+	auxiliary will	+	auxiliary have	+	auxiliary be	+	main verb
		invariable		invariable		past participle		present participle
		will		have		been		base + ing

For negative sentences in the Future Perfect Continuous tense, we insert not between will and have. For question sentences, we exchange the subject and will. Look at these example sentences with the Future Perfect Continuous:

	subject	auxiliary verb		auxiliary verb	auxiliary verb	main verb
+	I	will		have	been	working	for four hours.
+	You	will		have	been	travelling	for two days.
-	She	will	not	have	been	using	the car.
-	We	will	not	have	been	waiting	long.
?	Will	you		have	been	playing	football?
?	Will	they		have	been	watching	TV?

We sometimes use shall instead of will, especially for I and we.

Contraction with Future Perfect Continuous

In speaking with the Future Perfect Continuous tense, we often contract the subject and WILL:

I will	I'll
you will	you'll
he will she will it will	he'll she'll it'll
we will	we'll
they will	they'll

• I'll have been driving for five hours.
• She'll have been watching TV.

In negative sentences, we may contract with won't, like this:

I will not	I won't
you will not	you won't
he willnot she will not it will not	he won't she won't it won't
we will not	we won't
they will not	they won't

• You won't have been drinking, will you?
• We won't have been driving for long.

How do we use the Future Perfect Continuous Tense?

The Future Perfect Continuous tense is like the Future Perfect tense, but it expresses longer actions or states extending up to some specific event or time in the future. For example:

• Ram starts waiting at 9am. I am late and cannot arrive before 10am. Ram will have been waiting for an hour by the time I meet him.

Ram will have been waiting for one hour when I arrive.
past	present	future
	Ram starts waiting at 9am.
9 10
		I will arrive in future at 10am.

Notice that the long action or state can start at any time in the past, present or future, but of course it always ends in the future.

Next Monday we will have been living here for exactly five years.
past	present	future
next Mon. 5 yrs ago

Look at these examples:

• He'll be tired when he gets here. He'll have been travelling all day.
• How long will Jo have been working when he retires?
• Next month I'll have been studying Chinese for two years.
• Will you have been working when I arrive?
• He won't have been studying long enough to qualify.
• Next week Jane is going to swim from England to France. By the time she gets to France she'll have been swimming non-stop for over thirteen hours.

Note that continuous tenses are also called progressive tenses. So the Future Perfect Continuous tense is sometimes called the Future Perfect Progressive tense.

https://www.englishclub.com/grammar/verb-tenses_future-perfect-continuous.htm