Supposing we could accelerate at 1g for half the duration and decelerate at 1g for the other half it would only take 7.3 years for the travellers, with 41.9 years passed on Earth. http://nathangeffen.webfactional.com/spacetravel/spacetravel.php

Except the best we can do now for sustained acceleration is a solar sail at about 0.001 m/s^2, or 1232 years. That wouldn't work ofcourse as that acceleration will go down to nothing once getting further from the sun. Yet perhaps with a powerful concentrated laser you can push a spacecraft all the way, then you just need to worry about slowing down.

http://www.zmescience.com/space/lasers-mars-travel-04232/ Very promising for probes:  “As an example, on the eventual upper end, a full scale DE-STAR 4 (50-70 GW) will propel a wafer scale spacecraft with a 1 m laser sail to about 26% the speed of light in about 10 minutes (20 kgo accel), reach Mars (1 AU) in 30 minutes, pass Voyager I in less than 3 days, pass 1,000 AU in 12 days and reach Alpha Centauri in about 15 years. Pretty amazing!

By the time we have developed faster space craft we would have achieved a far higher level of A.I. and we will end up sending robots instead I think then the data will be sent back as some sort of interative VR experience (mapping areas etc) for humanity to enjoy risk free. Can't see humans making it to the stars for a long time. Even if you want to colonise it would be better sent as DNA with special breeding/growing equipment. The DNA will likely have to be modified to fit the environment so no point sending full humans anyway. We are thinking too much at our current 21st century technology level not what will be achieved a century or more in the future. Mastering DNA and huge improvements in A.I. are I think easy predictions for the future.

I hate to get all environmental on these exciting subjects, but humanity will never reach an age when we are capable of achieving the speeds and technology to reach these goldilocks planets. At the current rate of population growth and the destructive ways we're using the Earths resources for power, food and for our lifestyles, we would of self destructed way way way before we manage. The human race will be reduced back to a sort of tribal state.

Imo looking for earth like planets to colonize is also thinking too much along our 21st century tech level. By the time we can reach ot that far we likely won't be restricted by little blue/green marbles anymore for survival. We're like cave man looking for any decent distant caves for future generations. I mean why would an AI raise fragile human beings from DNA once there. As a pet project? Hmm where's that AI hiding out nowadays...

They would be programmed to raise human beings as their purpose  and once enough have been created they would start naturally reproducing a larger human colony and I guess that may be possible with robots in the future too. Manufacturing robots that can replicate themselves and other machinery needed for colonisation. I can't see much being transported from this system to a far away system and the time period would be so huge anyway that by the time they get there the people who sent the colonisation craft would be long gone.

I can't deny the possibility although not sure why you say tribal state there would be a real chance we would eradicate all life on the surface of this planet or at least take life back to a bacteria level on this planet. 

I'm thinking more along the line of once we have working AI, we'll also be close to transferring human consciousness or replicating it closely enough. Why sail all accross the ocean to settle in a cave. Why go back to fragile forms when the universe is open to explore without such limitations. It would be like putting a little zoo down on a planet.
Ofcourse there will be traditionalists, like we have Amish societies right now, yet growing humans on a distant planet seems kinda pointless once robotics and AI advance far enough to actually be able to do that.

Great news! :)

One of the Scientists said that in a few years they will have enough dada to know if life is already on those planets 

Survival of the species I suppose. I guess ultimately that's what instinctively its all about, spreading our DNA. We can't kick alien arses (assuming they have arses) without legs. Organic life can multiply with basic water, carbon etc. I guess we can design organic robots using DNA though thinking about it. Once you completely master DNA you can design anything you want to, be it a flock of dentist chairs or a whoop of electric guitars etc.

True. Greg Bear's Hull Zero Three describes such a colonization ship. Tailoring DNA to whatever is needed at the time for the conditions of the target planet(s). Yet once we master energy and matter manipulation, organic life becomes very restrictive. If you only need energy and raw matter to survive, and perhaps even only energy at some point, why bother with organic DNA. It would explain why we haven't detected alien life yet. No Dyson spheres or Ringworlds or other terraforming projects etc spread all over the night sky. By the time a species reaches long distance space flight, the need for corpereal forms and giant self sustaining organic habitats might be obsolete.