Space colonization will be possible within the century. If you're optimistic, maybe before 2050. The idea is feasible, it just needs more research and support from governments in the world. As they work towards it and convince the public at large that it's beneficial to move upward to the stars, private industry will regulate and monetize the process. It won't be perfect but it will get people out there. It's anyone's guess how space-faring societies will go. Sea colonization, I can't comment on. I know there's a lot of work going into topside structures that can sustain themselves but I have no idea if we're going to have a Sealab by 2020.
Transhumanism is happening, sure. It's a fringe idea now but only because the public support for such ambitious goals is always precarious at best unless laden with spiritual and religious themes. It's completely feasible and in the next few decades the secondary goals of it will be met. Transhumansim isn't too well-defined I think because every organization dedicated to it has a slightly shifted idea of what it should be. Some think it's to completely eliminate suffering from the human experience. Some see it as a simple pro-technology ideation and devotion to augmenting human ability. Some think it's just an edgy scif-i motif that looks cool.
For ease I'll use the more grand but less definitive idea: to eliminate human suffering. The goal of transhumanism is to progress with the help of technology. To become the masters of the world around us and defeat things as precarious as death, aging, depletion of resources, poverty, etc. It's extremely idealistic, to be frank. That said I think it's an important idea and I think it's not nearly as new as people make it out to be. Humanity has always been one to take the world around it and transform that world to its will. We suffer for our mistakes in doing this but it's fundamentally human to manipulate the world and carry on. The only difference now is that we are approaching somewhat of a singularity wherein there's almost no telling how it's going to play out.
This next century is going to make or break us, I think. We'll either take to the stars and look onward to the edge, examining what it means to be human, or we'll kill each other over clean water and natural gas until the world is so caked in ash that we finally die off. We're not special just because we're alive, though. There's no plot armor on our species and the only way we'll survive is by realizing that. I tend to veer between two mindsets when I think about this. The first is optimistic about the technology we have and the ideas we can produce and make into reality. That spirit has been with us forever and guided humanity to where we are now. The other mind I keep on this is pessimistic: we are on the very edge of it all right now. We just exited the most dangerous time to be alive because two governments alone held the capacity to destroy everything we've worked toward, and now we're sinking right back into that. Only difference is now we also have to contend with the extreme ecological shift we're producing due to our ignorance concerning the environment, and we are as a society consuming way too much. What's the solution to that?
It seems simple and in some ways it is. The problem is that we all have an engendered arrogance when it comes to this stuff. Everything moves so slow because people never want to believe they're wrong and because of that we have wars over dick-swinging, and we have environmental catastrophes because no one wants to admit things need to change. No one wants to put down their steak and their white-picket fences and their endless suburbs but somewhere in the next few decades they're going to have to make an extreme change in the way they live. It's either that or everything ends because they wanted more meat and SUVs than we could squeeze out of the world.
I'm not saying this to scare-monger. I'm an optimist when it concerns technology. It's just that the same fundamental power we have to manipulate the world around us also gives us such an extreme, debilitating arrogance, that I wonder if we'll really make it. If we establish humanity outside of the planet Earth then we have a good couple hundred million years where it's almost guaranteed that we'll survive. We could destroy civilization hundreds of times in that time-frame and be fine. We basically have a blank check from the universe that we'll always be able to cash in. The problem is just getting our asses off of this planet before we make it uninhabitable to us and we choke on the fumes of it all, staring up into the sky and wondering at what could have been,