TL:DR, only read the first page.
I think we will eventually reach alpha (dang, I can't spell it, never could, and dont wanna look it up) but I am not sure about HUMANS reaching it. If I recall, there are 2 space shuttles that were launched which have both cleared the Termination Shock, but not sure if they are heading in the right direction. Their goal, I believe, was to search for life. As for humans on alpha centari (? am I close enough?), we'd need something like Civ4 has, with a statis chambers to prevent aging, because no humans could possibly survive reaching their with current shuttle speeds, and I doubt we could ever travel light speed (we still would take years at lightspeed). Even if they go there though, there's no guarentee of life, or even survivable planets.
As for a possibility of a nuclear war, I dunno, but I should hope not. At the moment, the world is in pretty much a stalemate. Every country knows that if they fire a nuke, they face getting nuked themselves. However, all it takes is one wiseguy (get smart, anyone?)... Also, it does raise a problem that terrorists who serve no country could use a nuke, and it would be difficult to retaliate since Nukes ALWAYS kill more innocents than intended targets. Humanity has had 2 nuclear explosions (not counting numerous tests) which each killed many civilians and few military personals (I never condoned US's nuclear attack on Japan, whether or not it made Japan surrender, because of the sheer horror of what the Nukes did). And advancements in technology have made nuclear bombs much much more powerful, easily capable of taking out a whole city, and leaving it a radiation wasteland for years.
Humanities future is impossible to predict, so I won't try to. Whether the future will be good or bad, nobody can say, though let's look at a few things:
It took thousands of years to go from the wheel to the automobile, but barely half a century to go from the automobile to space travel.
Some of the most deadly conflicts occured in the past 100 years. The two world wars caused more casuallities than any other, and they were using primitive technology. Imagine a world war today with nuclear bombs, jet fighters, advanced tanks, and more. Weapons have evolved to the point of being so deadly that it makes one wonder if a world war would whipe out humanity as we know it.
I can't recall who, but someone said "I don't know what world war 3 will be fought with, but world war 4 will be fought with sticks and stones".