There could be planets that support life that are orbiting our nearest star. If so, the 43 year trip is certainly possible, especially as human lifespans rapidly increase. Send 25 year old astronauts and they will be 68 by the time they arrive. Of course they may not live long enough for the return trip(they would be 111+ years old) so it's going to be a lifelong trip for them. Of course the females can procreate during the trip.
It may be possible someday to cryogenically vitualize(non-freezing solid state) someone and reanimate after 500+ years. This will allow a 50 lightyear distance. Of course it will still take 50 years each way to transmit information at light speed(unless they find a way for FTL communication) but this will still allow humans to spread out and colonise other planets.
No one knows if FTL travel or even communication will ever be possible. Even if not, humans can still travel to the nearest stars and planets, populate those planets then travel yet again to the next nearest stars and planets. Just like plants slowly spread over generations to nearby land(they produce seeds that fall a small distance away), humans will do the same. After millions of years, humans can populate the entire galaxy and millions more years to populate neighbooring galaxies! 
