Why would anyone from the future want to claim that they are from the future? It may effect the future so much, any idiot would know not to do that.
I'm pretty sure that it will be impossible to ever create some sort of time machine no matter how advance our technology is. Like i said before, unless somebody travels back in time to a place where there is no entities around can there be an identical future. Nobody would want to mess up the future. Thats unless a guy destroys earth and you have to take on the task with your time machine to make sure he was never born.