Speculation

- the forming of a theory or conjecture without firm evidence.

"Most of the scientific community believes that, at the moment, cryonics is just speculation."

similar example:

• there has been widespread speculation that he plans to quit
• He dismissed their theories as mere speculation.
• The book is just a lot of idle speculation about the future.
• Her speculations leave many questions unanswered.
• He lost everything in foolish land speculation.