Yes
The Future Is Unknown was created on 2004-03-28.
It is correct to use "which is" when talking about a singular future unknown situation or option. If referring to multiple future unknown situations or options, it is correct to use "which are."
It is unknown what the future holds considering technology.
That is unknown. What it happen in the future is not known.
Unknown
The future is unknown.
It is unknown if computers will replace books in the future.
It is unknown as the series does not go that far into the future.
It is unknown as the story doesn't go as far into the future as that.
Maybe. Although it's unknown
Probably... But still in the unknown future (means he isn't hokage yet)
Yes.