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."
Yes
It is unknown what the future holds considering technology.
Sender Unknown was created in 2006.
That is unknown. What it happen in the future is not known.
Journey to the Unknown was created in 1968.
Voyage into the Unknown was created in 1984.
Unknown Africa was created in 2007.
Birthplace Unknown was created in 1988.
The Fringe of the Unknown was created in 1983.
Giant from the Unknown was created in 1958.
Lurking Unknown was created in 1967.