Eh, I agree with the post you're disagreeing with.

It could be we develop some new physics soon and hopefully the engineering know how to take advantage of it. In this scenario we've developed space travel with a still primitive understanding of human biology. A far more likely option in my eyes (although still very unlikely as this is all speculation and opinion) is that we eventually develop a way to move into the transhuman era and robot ourselves. At this point space travel can use the traditional method of traveling < speed of light although this isn't interesting. Also, if you can upload your mind onto a server, I wonder how much value you'd place on exploration. Of course the singularity concept is just SciFi right now and probably just as likely as us developing wormholes, but it seems like it should be more likely given another century or two.

See, I think we could make generation ships with current-ish tech, and travel the stars, really really slowly. I mean, it would be a huge effort; it would be a really difficult engineering problem, and the ships would be easy to wipe out, but it would still largely be an engineering problem that could be solved, mostly, with the science of today (and a whole lot of time and money)

I think I'd put "uploading" in the same category as 'faster than light travel' - lots and lots of breakthroughs in fundamental sciences need to happen before we get either one of those things. (FTL travel feels less squishy to me, but that's just because the problem can be defined in a less squishy sort of way. I see no evidence that it's actually easier) -

I agree with your second paragraph that any concept of uploading is inherently squishy as we don't even understand the problem domain well enough to show how to do such a project.

As far as colony ships go, I think it would be hard to feed people for a couple of centuries, keep the systems running, and keep the passengers from going insane. It would have to be very big for even a few people in my mind for the agricultural requirements.

Colony ships would be massively difficult. Maybe even impossibly difficult? but the impossibility would be in the details and the effort. We'd be designing a very complex, very touchy system full of parts that could break. But... I'm just saying, there's nothing in our current understanding of science that makes it impossible, like faster than light travel, and the goal is clear; we'd know it when we finished it, unlike uploading humans.