Do you think we can really live in space?

If you mean living on planets in space, without space suits as such no. If we had to take a shuttle and float around in space, or as you said build space colonies and make sure that we can get a supply of oxygen then yes. However, if the earth goes we can't live in space because we only find oxygen in earth, and in space there is no oxygen and if we can't get access to oxygen we will die. One, as long as the earth exists, can live in outer space as long as he/she "refuels" for oxygen.

It depends on water on space, Life depends on water, if there is no water, how can we live there? So it is not possible to survive there for long time.

Well, I think if we see that we couldn't live on Earth anymore then money would go out the window and everyone would work their butts off to find a way to start a colony in space. If our planet were dying, then it would make sense that no one would want money to build something that can save everyone's lives. It may be hard, however, to find a quick way to get into space and start living there. We would need a way to get a whole lot of people into space, and then we would need a way to keep them living on another inhospitable planet, which is definitely a difficult thing to do.