Let’s say we left one single very smart guy (not necessarily with the knowledge: they may be able to understand hard stuff when taught it, but not know it already) alone on a copy of the earth. That person is also immortal. Could that person, by themselves, gain back all knowledge, maybe also experimental, or even surpass that is already available to us right now, before the planet gets inevitably engulfed by a sun turning red giant?
While I know that infinity means infinity, I think that like fractals we tend to move about one point instead of trending away at random. I wouldn’t change radically over time, I would just become a more complex self-similar being.