A lot of people I know say they don't want to live forever. They say mortality is part of what makes us human, and some people will add that 'God did not mean for us to live forever'. I say bullshit.
Recent advancements in technology have allowed us to understand more and more about (in my opinion) the two most important features of humans: the brain and the genome. Understanding the genome helps us understand how our biological bodies work, and it gives us the possibility to increase our maximum age well beyond our current lifespan by preventing diseases (like cancer) and strengthening organs (like the heart). It won't be long until cloning replacement organs will be commonplace. A further understanding of the genome also allows us to develop better technological alternatives to biological organs that will far outlast our current organs.
But the most interesting development is the simulation of the human brain. IBM is working on a project that can simulate a human brain, and they're not far off from succeeding. Imagine the possibilities available to us if we can make an exact copy of all the information in a human brain. While some might argue that a person's soul/self/core/whatever is something more than just the sum of its parts, I fully believe that human beings are just neural networks, and that capturing whatever is in the brain will allow us to create a perfect copy of ourselves.
I'm inspired to write about this because I'm reading a book by Ray Kurzweil called The singularity is near, wherein he predicts that, this century, an event of such great impact will happen that human beings have no way of predicting what life will be like after it. The main reasons he cites for this are the advances of nanotechnology, robotics, and the understanding of the human brain and genome. I think there's a fine line between being a brilliant visionary and a mad witch doctor, and Kurzweil is certainly on the edge of both. In my opinion his book is a bit too extreme in its predictions (other people agree, see the wiki article), but the fundamental idea is not wrong.
In this century there will be great advancements in technology and the understanding of the human body and brain. I believe this will allow my generation to extend our biological life by many years, and I think it will be long enough to last us until we are able to create a perfect copy of ourselves using technology. Even if that copy will only last us for one hundred or two hundred years, and it will not be available to everyone based on the world's economical and political conditions, the point is that 'mankind' will have achieved immortality from that point. From that point on life can be seen as we see computers now: make regular backups, be sure not to catch viruses, and upgrade your hardware and software every once in a while.
Obvious arguments at this point are that there will be an explosion of the population growth, and the earth will not be able to sustain an ever-increasing human population. I think there will be solutions for that. Smart solutions that will have to change the way we think about life. Let me propose some crazy things here that we will need to consider (but that I don't necessarily agree with!). Imagine digitizing every human being in a poor country and running them inside a computer simulation instead. That would certainly decrease energy requirements. Or we could just turn them off until we have the necessary energy to activate them. What about merging people with similar brain patterns? If two people are so much alike that they're digitally nearly indistinguishable, how about merging them? Once the human brain is digitized, everyone can have the same potential. We can learn the same things, become excellent at the same things, just like loading a program. What if, after one thousand years, everyone has learned everything available in our centralized knowledge base? Perhaps we will all be the same. If a neural network of a certain configuration is trained time and time again with the same data, it will adapt to the data perfectly. If we all have the same (optimal) configuration and if we all share the same data, won't be all be the same, eventually? I look forward a great deal to observing if mankind will face these problems, and how they will solve them if they happen. I plan to live forever.