If these are immediate responses then "did you mean" is not usual There also seems no reason to use "would". You can say "Do you mean it's not sure yet if it will happen?". "it's not sure yet" is passable in conversation, but seems slightly iffy to me in more formal English. You could say "it's not certain yet". In other contexts, such as "I'm not sure yet", the words "not sure yet" are fine.