Usain Bolt 9,69 seconds

Now that the world record for the 100 metres has been broken and set at 9,69 seconds, there must come a time when it is no longer possible to break, the absolute limit of human endeavor. My father in law, who is a retired sports teacher thinks that this limit will get to around 9,5 seconds and after that will never be broken again (drugs free) and will stand forever. What do you think?
Matt
Matt