Here are some important questions:
0. What does it take for a person to exist?
1. What does it take to keep a person in existence?
2. What does it take to keep a person alive?
3. What does it take to keep a person conscious?
4. What does it take to keep a person in control of his mind?
5. What does it take to keep a person in control of his body?
6. What does it take to keep a person happy?
We need to answer to all of them, in the right order. The answer to every question is necessary for the next.
0. It doesn't really matter to me, as it's not something that requires maintenance. I either exist or I don't. It looks like I exist, so this question will never matter to me (assuming I'm selfish and others don't have to exist).
1. I prefer my body to be preserved than not. Hopefully, we will reach the point where I can be revived.
2. Being alive is nice and all, but it's not pretty exciting. Want to be in a coma all your life? Probably not. Still, it's easier with current technologies to bring consciousness to someone in a coma than to bring life to a dead "preserved" body.
3. Now you're talking. I like being conscious. Without it, it's like I don't even exist. But passively feeling the world has its limits.
4. Control of my mind changes everything. I'm no longer limited by the external world, I can imagine my own. However, this also brings the ability to suffer, which I don't believe is present with consciousness alone (a world in which there's no good or bad). In that state, The Matrix would be enough to entertain me for a while. Unless it's not.
5. Well, now I can actually change how the world works. Sure, you could argue that I already could when I was able to communicate with The Matrix, and you would be right. But I make a distinction here, just because. At this point, you have some control over the above, and you can actually be in control of your fate, life and future. This is probably where you reach a point where you start automating the above conditions, and build the infrastructure to keep you alive/conscious/active/etc.
6. Now that's the hard question. To exist, to be alive, to be conscious, it's not really subjective. Most people would agree about what it takes for these conditions to be met. But happiness, that's a hard one. Excluding all of the above from the scope of happiness might help. Being healthy, conscious, able to think, are all necessary for happiness to ever be considered, so we don't have to think about them. We must think about art, love, family, etc. These are all things that are not necessary to exist, being alive, being conscious, having control over his body, etc. Why do we need them? Why can't we be happy once 1-5 are fulfilled? Is there a need to reproduce, as a backup in the case that the system fails and people cease to exist? Are we more happy when we're more people? Are we more happy when we have more resources to maintain the conditions above? Should we measure happiness as the predicted time left to live? Is living in 2013 worth less than living in 2020 (in which case, it would make sense to cryogenize someone and defrost/revive him in the future)? Don't we do it because it's too risky (we still don't know what might happen when we lose control)? Is loss of control the main fear we have?
I want to live in a world where 1-5 are taken care of. They're objective conditions, they don't change from person to person. At this point, we will be able to reflect on life, and build a future where we can be truly happy. If that's possible.