If you ask people "How old will you live to be?" you will get many answers. It is unlikely that anyone will say "200" because no-one has ever done that.
I am sorry. Let me narrow down the question. I ask my friend how old he thought people would live in the future. Maybe in 200 years, how old will you live to be?Here is a share of words all like, being imagine, will, also hope, wish, and shall. Is the meaning of your question 'imagine', 'wish', or 'hope'? That answer is a jest to any question but 'How old do you wish to be?' or 'How old do you hope to be?' As was said it has not been proved by record that any man has lived for more than an hundred years about. It is right that will and imagine are alike, and understand that you could change that line to 'How old shall you live to be?' and it would mean the same.
But When you ask with how long, you can only get a length of a time but the answer in OP is about an age, am I right:Your question only makes sense if 'you' is used as an impersonal reference to a person, such as 'one'.
If that was what you mean and the context supports that interpretation, your friend might answer with whatever age he thinks people will achieve in the future.
However, if that is what you mean, the use of 'you' is confusing. It would be better to ask, "How long will people live 200 years from now?"
Got it. Thank you so much! I am so sorry for confusing people here.You're making the question very confusing, Sun-14, by using both "200 years from now" and "200 years old."
You appear to want to ask about human life expectancy two centuries from now, and to know whether asking "How long...?" could elicit the response "...live to be 200 years old" rather than "...live for 200 years." I think either response is possible, though the latter is more likely. To get the former response, you could ask "How old do you think people born 200 years from now will live to be?"