I think bitcoin will exist as long as the internet and the brains behind those computers exist. The truth is, there is a limit to everything, there are two possible outcomes of bitcoin. First if bitcoin became famous, it will forever live just like facebook, twitter and etc. Bitcoin will only improve and upgrade then, but if it will not last long just like other organizations and businesses, it will be forgotten forever. Though it is hardly the outcome of bitcoin, nothing is still impossible to the web. So I think if tokens became outdated as the times goes by, I think bitcoin will use alternatives and will not let bitcoin die because if they let it happen, their biggest business will also vanish.