Some thoughts for consideration:
- Within 50 years (if not much sooner), we'll almost certainly have cured aging. Once humans regularly live in the many hundreds (or even thousands) of years, a 20, 30, 50, even 100 year trip won't seem as long (plus we'll have great on-board entertainment to keep us busy thanks to advanced robotic girlfriends).
- Once you approach even half the speed of light, local time slows down for you, so e.g. a 50 year trip would be 'only' 30 or 40 years (I haven't done the exact math)
- Accelerating humans to half C won't be easy, but if you consider that aging may be cured in our lifetimes, the goal of sending autonomous robotic explorers to stars (a la Mars Curiosity) just 13ly away may be quite feasible in some of our lifetimes. That alone is exciting. If you live 500 years, and you send a robotic probe at 1/10th C to a star 13 ly away (130 year trip plus 13 years for data to come back), you'll EASILY live to see the results. And beyond that, who knows - the technology of 150 years from now, we may well be sending the first humans to the nearest stars by then.
This is not even 'inane fantasy', it's just what is likely to become possible, and even to become mundane reality.
My suspicion is that we'll never find a way to travel faster than the speed of light. But our discussions seem to be limited by a common inability to imagine that other variables, that we take for granted, may change dramatically - e.g. the typical human lifespan.
Also, perspective: We've been 'human' for approximately 2 million years. We have millions of years ahead of us as a species, and even on cosmic scales, you can do an enormous amount in even just 2 million years.
I'm cautiously optimistic. I think our future in space is practically certain, and that we'll probably ultimately reach hundreds of other stars, and establish colonies on other planets. It's a matter of when and how, not if. The only thing that can stop us if everyone collectively gives up. That isn't going to happen, there will always be humans who want to explore.