Posthumanity is definitely an area within the game. It's not prohibited by the laws of physics. The relevant questions are how difficult it would be to achieve and whether it would be enough fun to be worth the effort.

Let's assume it's worth the effort, and consider how difficult it is.

The mere fact that it's physically possible contributes negligibly little evidence towards believing it to be practically possible; strictly speaking it's equivalent to saying the probability of success (of achieving posthuman existence) isn't zero. That's true but is a very weak, non-informative claim.

A lot of desirable things are physically possible but unreachable for all practical purposes. They may be inherently improbable (by relying on processes objectively improbable to succeed) or they may require knowledge we don't have and don't know at present how to acquire.

For instance, I believe there's a series of simple actions I could undertake - speaking to people and so on - that would make me very rich, or powerful, or very well-connected. There is certainly nothing physically impossible about it. But I have no idea how to locate the concrete series of actions in the huge space of my physically possible actions.

So what interesting evidence do you have that :"posthuman" existence is realistically achievable, for us who are alive today? More importantly, do you have any evidence as to what actions today would help us achieve it in the future, beyond generally living as long as possible and amassing a lot of money and other resources?