Writing about the future is, in a way, similar to writing about the past. In historical fiction, where you have facts you should stick to them reasonably closely (unless you're Phillipa Gregory of course). Wherever there are holes, you can pretty much write whatever you want, so long as it doesn't contradict the facts. I think you should go by that principle here. Don't stray too far from the science, but beyond that you can be a bit creative. What's unethical about that? Don't worry about being labelled an alarmist. That's just a lazy insult thrown about by people who don't like what they hear but can't come up with a proper reason why.
The obvious follow-on here is that the future, by definition, has more holes than the past. It doesn't exist yet, and therefore can go in infinite directions plausibly within the laws of science (or, frankly, outside them if you're writing space opera).
