It more than likely will happen way beyond our lifetime. Which begs the question, why haven't we been visited by time travelers? And if we have, would we even know about it? Would they even be able to visit this "past" or some other parallel past? For other theories that have been now recently proven, read up on the Einstein Condensate, and the status of quantum teleportation.
That was exactly what I was thinking - if time travel becomes possible at some point, why haven't we been visited by time-travellers?
My theory: more than one reality can exist at the same "time". The instant you travel back in time, you're initiating a new time line from the instant that you arrive. A,B, C ..... F. Travel back to point C, and you begin a new line C1, D1, E1, F1. My theory is that C, D, E F still exists despite your time travel creation of C1, D1, E1, F1. In other words, you aren't really destroying history by traveling back in time, rather you're creating a brand new history. We aren't aware of time traverlers because their time travel creates a new reality which doesn't preclude our reality.
Not sure if time travel exists. But I am sure of one thing, if you can travel faster than the speed of light, you could see the past or future. Brain waves is the only element that could travel faster than the light. I have personally experienced meditators who knew everything about me, about my past and even told some of my future very accurately. And amazingly, I barely had to talk to him because he was reading my mind the whole time while we were chatting. Have you experienced dejavu? That's seeing the future before it came. If you have a spaceship that could travel faster than the speed of light, you pilot it, far far away and look back to the earth, you will see Dinosaurs. No joke.
As mentioned before, there would be only time-space observer, therefore time traveller would not exist. That means only A/B/C/etc exist that would never change. That a time-space observer, like a ghost or spirit, could only observe spiritually, but could not make any changes physically at all. There should not be another set of new events caused by a time-space observer. Otherwise, the universe would be a really chaos due to the multiplying effects caused by various travellers. Hence the things/people surrounding the time traveller while in the past should be also included/considered, as some of the people might as well time travellers dynamically. Everything/everyone besides the time traveller could not be all static. In simple words, our history could not be changed at all.
If C1/D1/E1/etc could exist, that means C2/D2/E2/etc as well as many other alternate series of events/facts could also (co)exist. When today's time traveller wants to visit a certain time of year/month/date, how does (s)he know which series of events/facts (s)he really wants to visit, while missing out other series of events/facts that (s)he might actually want to visit for a certain specific reason? He may not even know or doesn't have any ideas of how many series for his options - could be approaching a great number and growing every moment.
The existence of many unmeasured states is already documented in basic Quantum mechanics. All possible states exist in theory simultaneously, but not in practice until one state is measured ( the act of moving back in time to point C, for example ). As we move forward in time in our day to day life , there are many possible states existing in theory until we measure a state ( make a decision. ). Of course, you will argue that by measuring one state we destroy all other states. However, is this true if we're travelling back in time, or do we return to the point where there are many unmeasured states? If you travel back in time, do you destroy your own timeline, or do you in fact create a reality where there are now two measured states? Its just a theory as I suggested above. I'm obviously talking a little out of my butt.
I am just unsure whether the concept of state in quantum mechanics (micro-structure) would be well applicable to when it is used in time travelling about historical events/facts along timeline (macro-events). Perhaps a state would be an event in a series/timeline of events. However, imo, state would not be the same as series/timeline. A series/timeline consists of a series of events. (Of course, an event has any states/status.) Maybe it should. But the potential of chaos due to unlimited optional events/facts/scenarios mentioned before could be still a problem, imo. Creating multiple/unlimited timelines or number-of-series. Returning/travelling to a wrong series/timeline at a certain state alone/of the timeline/series may lead to the unexpected subsequent events that the traveller might not want to visit as originally planned.
Btw, if history can be cganged, can someone travel back to the time/moment when there was only one single human being and physically destroy that human? Then there would be no human afterwards at all, even nowadays. All humans in our history would suddenly disappear completely! Great!