1.) we are imagining what language will look like in a fictional future society. how language "works" is certainly up for debate no?
Human behavior and psychology aren't going to randomly change in the future. The way you extrapolate the future is by understanding the past and the present and projecting forward. The future isn't some magical fairyland where anything is possible, it's just the present that we haven't caught up with yet. I mean, we're in 2017. That was the distant future when Star Trek was new. And human nature hasn't changed that much; we just have a few new gadgets to play with, although not the same kind of gadgets they thought we'd have back then. (According to "Space Seed," the interplanetary sleeper ships we've been using for the past two decades are due to go obsolete next year when a faster space drive comes along.)
you think its simply impossible that a one world government who spearheads a federation of planets may lean on one language over others?
As I said, only a tyrannical, oppressive government would attempt that, and it would meet with ferocious pushback from from the cultures whose linguistic heritage was thus threatened. Study your history. Read up on the way Native American communities reacted to the US government's efforts to eradicate their languages and cultures. They'd play along superficially, but they'd privately cling to their own languages all the harder, continuing to teach them to their children and use them in secret at home. So languages and cultures that the government believed to be eradicated were actually clinging onto life as an act of defiance, and that's why they're still around today.
Also, you're persisting in the totally false assumption that having one global language would require eradicating all other languages. As I said, that has never been the case. It's not an either/or proposition, because most human beings are bilingual.
i dont think diversity in that future would like "lets make sure we have an even mix of this that and the other. i think by then everyone is accepted as equal and people have pure equal opportunity. no effort towards diverse recruitment, no walls in the way, chips simply fall where they may.
There is absolutely no way in hell that that premise could lead to a world where every language but one has ceased to exist. On the contrary, if the chips fall where they may, if there's no conscious effort to impose an unnatural monolingualism, then of course multiple languages will continue to exist. There will be a lingua franca used globally, much as English, Spanish, French, and Chinese are already used internationally today, and there will be many other languages used locally. That's the way human communication has worked for thousands of years, and it's nonsensical to expect that to suddenly change within the next measly 2-3 centuries.