All of your examples are acceptable English and would make sense, but a native speaker almost certainly use any of them. A native would say something like "We don't know." or "We're not sure.".

I know that you'd prefer to have the answer begin with 'it', but I think starting the answer with 'it' seems rather awkward. Like Nathan said, most natives wouldn't answer that way. We would say, "It's unsure/uncertain right now", but more naturally we'd answer, "That hasn't been determined", "We don't know yet", "That's unknown right now". I think the reason for this is because you are speaking of an event for some time in the future. It becomes a this vs that issue. You are talking about 'that' event which has not yet occurred (it's something over there or far away) vs 'this' even which is occurring or very close to occurring or here now.