FUTURE PERFECT CONTINUOUS
This form is composed of two elements: the future perfect of the verb to be (will have been) + the present participle of the main verb (base+ing):
Subject will have been base+ing
We will have been living
Affirmative: I will have been working
Negative: I won't have been working
Interrogative: Will I have been working?
Like the future perfect simple, this form is used to project ourselves forward in time and to look back. It refers to events or actions in a time between now and some future time, that may be unfinished.
I will have been waiting here for three hours by six o'clock.
By 2001 I will have been living here for sixteen years.
By the time I finish this course, I will have been learning English for twenty years.