SingularPlural
I will have been walkingwe will have been walking
you will have been walkingyou will have been walking
he/she/it will have been walkingthey will have been walking

SingularPlural
I will have been sleepingwe will have been sleeping
you will have been sleepingyou will have been sleeping
he/she/it will have been sleepingthey will have been sleeping

SingularPlural
There is no future perfect progressive for the "to be" verb. "Will have been being" is expressed simply as "will have been": "By this time next year we will have been being on this committee for a decade."