I feel the three most important issues that scientists should address are as follows:
1.) Light speed travel - we will never be able to explore the universe and find a new home to destroy without the ability to travel greater distances with less effort. To me this is one the most important aspects of human survival. If we do not achieve light speed travel our existance could be cut short relatively quickly. I don't know about you but I would like to see humanity contintue to evolve far beyond what were capable of now. Call it my Star Trek fantasy but I feel it truly makes sense. Spock feels it's logical...
2.) Cures to all disease - I hate that peoples lives can be cut short so quickly because we don't have the medicine to prevent or treat life threatening conditions. My grandfather died a few years ago after having surgery to clear a clogged artery in his neck. Doctors found the problem during a routine checkup. He was fine until he had the surgery. Then he died a year after it because doctors couldn't figure out what was wrong after the surgery. He lived a good life but he could've lived an even better one if we had the technology.
3. ) Organic Digital processors - Technology will not continue to evolve until humanity can engineer a self evolving orgainc digital processor. Moore's Law will be humanities undoing if we cannot evolve beyond it. This is key as the technologies required for humanity to achieve great things is hinderd by our inability to move beyond silicon. Moore's prediction has held strong for far too long and humanity needs a boost. World governments need to set their differences aside, combine resources and technology in name of evolution of human kind. Unless we get our heads out of our rears and move forward we will be doomed.