Second, does it really matter at all if our artificial replacements can play with the cosmos? To me, human actions and their motives boil down to survival and happiness/the avoidance of unhappiness. I think it's possible to create a wonderful world right here with most of the technology we have (actually, with most of the technology that existed centuries or millennia ago) without eliminating the human race and replacing it with a bunch of digital imitators. I think that this endless quest for more technology, money, and stuff is intended to promote happiness, but that it hasn't really worked. Else, people today, having more technology and stuff, must be living in a state of continuous orgasm, while earlier people must have been perpetually depressed and suicidal.
That's obviously not the case. People are animals with animal needs, and I'm not just talking about food and water. Just as horses need room to romp around and a herd to live in, and just as cats need something to hunt or chase to be happy, so do people have their own particular set of basic psychological needs in order to be happy. A sense of being a valuable and accepted member of a community, the sense of community itself, companionship, exercise, a sense of purpose, methods of self-expression, something to wonder at--these seem to be some of those fundamental needs. It's entirely possible to be completely content in the Paleolithic Age or medieval Siam or modern America. The Amish are a testament to the fact that more technology isn't always better. Sure, their lives aren't perfect or necessarily better on the whole than ours, but they aren't automatically worse just because of less tech, either. Toys nowadays may have all sorts of components that make noise and move and so on, but as a kid I always had the most fun playing with toys that did nothing, like toy soldiers or planes. They require more imagination, and there are more possibilities with them. Hell, my friends and I often played army and went on adventures without the help of any toys at all. We could imagine everything. My point is that the basic needs of humanity haven't changed.
Now, technology can be used to solve some of the obstacles to these things, especially medical technology. Disease is the worst enemy of humanity and always has been. It kills many and can make the rest miserable. It has to go, and technology's good for that. Technology that can be used to prevent famine and poverty is also wonderful. Many more of our problems, such as overpopulation, war, crime, and general meanness, can't be handled by technology alone, if at all, and require people to act differently. I think it's entirely possible to solve these problems or at least greatly mitigate them without giving up and letting computer programs replace our species. We've just been barking up the wrong tree, losing sight of our goals and desires, and getting sidetracked. Technology will help achieve a lot of our goals, yes, but it isn't an end in itself, and we've been misusing it pretty often and forgetting what it's supposed to do and what our real goals are.
I'm very concerned that in their quest for more stuff, immortality, and an escape from their identity and nature (all of which is only meant to maximize their happiness like any other activity), people will actually end up unintentionally wiping out the human race or at the very least making happiness difficult if not impossible to pursue for those of us who don't actually want to participate in their quest. Posthumans/transhumans/digital copies of humans might even despise what they regard as inferior meatsacks and kill us off. Though, as I mentioned earlier, it's also possible that they could instead just put their physical components on some barren, uninhabitable planet and go "live" their simulated, digital existences there without having to interact with the physical world.