The idea that we can be completely rational creatures kinda conflicts with the fact that we are emotional creatures as well, and those emotions can sometimes over ride rational thought. As a species I highly doubt we will never assemble as a society without any forms of divisions, be it political, philisophical, emotional (jealousy/envy is a common one). As such we might eliminate religious irrationality, which in itself does quite alot of harm per se, however eliminating the emotional irrationalities would really seem an improbable task.

I think religion can never be eradicated. Which is a shame. We could have all the proof possible to show that God's existence isn't solid but religion would continue as it is based around faith. Faith cant be overridden even though its false. For example when we unearthed dinosaur bones, religious types said "God is testing our beliefs" I believe the same can be said when we prove God doesn't exist because faith would indicate to religious types that God yet again "is testing our beliefs"

But yes I agree that we'd only find other ways to separate ourselves. Racism will always exist, i'd like to think we can live together in harmony but that would be unlikely. Were intellectual but still very primitive beings and we'll try to separate ourselves from others. So there would still be conflict but the benefit of there being no religion is that people would know the truth and people would realise there is no afterlife and perhaps try to cooperate and live life to the full before it ends but obviously there will be people who do the opposite and cause conflict when they realise we exist by chance and life has no set purpose.
 

I think it's possible that given enough of a time frame, and with enough effort from the more vocal opponents of faith, religion will shrink to a minority. We might blow ourselves up before then, or get hit by a comet, but assuming we make it for a couple thousand more years, we'll eventually get there.

Of course, we may still have just as many problems, only they'll be different problems! Maybe worse problems!

As for the rational part, no way. Being irrational is instinctive. It's in all of us. Irrationality has as much chance of being eradicated as sexual desire, unless we evolve out of it somehow.

So maybe it is possible, by prolly not. Prolly not.