That could be a problem..... But the human race is adaptable.
In all seriousness I think the next big evolutionary leap will be the ability to transfer a human brain to a computer. In fact I think its probably more likely that real success with AI. That really opens up a whole new realm of possibilities.
A 50 or 100 year trip becomes a meaningless concept. You could send a ship full of human brained robots with thousands of frozen human embryos. The Robots could raise and teach generations of humans upon reaching the destination.