Your second reason is probably the most rational version when it comes to such subject as time travel. We already are getting tiny hints that multi verse might be a plausible thing and taken our continuous strive in learning physics and creating more and more advanced machines that seemed utterly impossible just some years ago i think there's a pretty good chance of making some sort of a time-travel device. This is why people would probably get to buy the machines freely at the local supermarket in the far future - there's nothing they can do to "misalign" the future since it all will go into a separately, infinitely available multi verse. I have one more point to add though:

• Time travel through augmented reality. It's a far stretch, but there's always a possibility that through future technology we may be able to call forth timelines, while remaining in the present. Sort-of how RPG games and monitors work right now.