1) There is no guarantee evolution will proceed to that extent. 1 million years is not that long from an evolutionary point of view (I personally would say that humans in the future will still largely be similar enough to us now in all fundamental aspects). Lets look at the reason they give: food, entertainment, and language.
I don't think I'd be wrong saying that every or almost every animal gets its energy in the same way on the molecular level. Unless literally everything that contains digestable compounds (amino acids, fats, sugars, etc.) that we can eat disappears, and we somehow lose the ability to synthesize these compounds (highly unlikely), you won't go hungry.
Entertainment is subjective. Shit some people get entertainment from exploring new areas. You can go explore the cosmos or if your more an indoors person, read a book.
Language is a tricky scenario and perhaps the only valid one, because it is hard to predict where that will go. I'm sure that even if you lose the ability to speak though you can still write or print. It not like not being able to speak is unheard of.
2)This point only makes sense assuming you're the only one with immortality, and then assuming my immortality wasn't from magic, but science, I'd give the scientists the secret.
3)I can't vouch for the brain functions of this part, but it sounds highly suspect and based on a misunderstand of science to me. That said, its no longer relevant, cause scientists have already developed/are perfecting ways to essentially make you forget information.
4)Even though time apparently appears to speed up as you age (mind you we haven't had a study with someone living for anywhere close the scale we're talking on), it is flawed to think that because a minute will feel like 6 seconds (to use the words of an article), you'll only get 6 seconds of "life" from a minute. You'll still be able to do everything you ever wanted to in a minute, its just a minute loses its significance since you aren't really constrained by time. Its a stupid point that has almost no scientific backing and is just plain speculation on the author's part.
5)A point that always gets brought up in these discussions. Here's the thing, any accident that would leave you trapped on a planet with humans is irrelevant since you could just get a small gps implant that would send you vital signs and location to your computer and if you indicate in someway (to the implant), to the police or any other authority. As for space, well sooner or later you're bound to hit something or enter something's gravitational field.
