Bitcoin can become useless only if people stop using it for some reason. In the short term, this seems unlikely, because not all people yet know what a cryptocurrency is. The technology of digital money is convenient, practical, has cheap transfers, therefore the society perceives it positively.
It can be useless at any time. For instance, imagine the situation when you own Bitcoin, but for some reasons, you find yourself in the place where the Internet connection is not available.
It's no use. Virtual money really needs a good internet network and not slow. If there is no network then you cannot do anything with your Bitcoin or other coins.