Future perfect continuous – passive
There are several reasons as to why we use the passive voice in English. In these notes, we’re going to focus on the future perfect continuous in the passive voice and its elaborations. Generally, we use the passive when the focus is on the action and NOT on WHO or WHAT is performing the action.
will + have + been + being + past participle (helped, known)
The subject is unknown. We don’t know who is the subject.
These artefacts will have been being observed in art galleries all over the world as the mystery as to who painted them still endures.
We use the passive to emphasise the subject.
By the year 2020, I will have been being studying for two years.
We use the passive to talk about general truths.
The earth will have been being kept on a constant spin for over 4.5 billion years by this year yet once again.
We can use the passive if we want to be unclear or vague about the subject.
Nobody has any clue as to who will have been being elected president during the 2034 term of the presidency.
We use the passive when the subject is irrelevant. (We don’t care who or what has caused the action to be).
These cities will have been being worked on for over five years by next month.
We use the passive in a more formal atmosphere like a thesis or an important piece of writing, especially scientifically speaking.
Languages will continue to evolve for the entirety of our lives and will have still been being spoken by everyone on the planet within the next century and well into the future.
Note that, the future perfect continuous (passive) is very outdated and could even be considered mostly archaic, although, this passive form can still be used and makes perfect sense.