Do you think the typical person advocating ecological balance has evaluated how the tradeoffs would change given future technology?

Good point. Probably not, and for some, their views would change with new technological options. For others (environmentalist types especially), they would probably retain their old views.

That said, the future-technology sword cuts both ways: Because most people aren't considering post-human tech, they're not thinking of (what some see as) the potential astronomical benefits from human survival. If 10^10 humans were only going to live at most another 1-2 billion years on Earth, their happiness could never outweigh the suffering of the 10^18 insects living on Earth at the same time. So if people aren't thinking about space colonization, why do they care so much about preserving humanity anyway? Two possible reasons are because they're speciesist and care more about humans or because they value things other than happiness and suffering. I think both are true here, and both are potentially problematic for CEV values.

Though if people without such strong intuitions are likely to become more rational, this would not be strong evidence.

Yeah, that would be my concern. These days, "being rational" tends to select for people who have other characteristics, including being more utilitarian in inclination. Interesting idea about seeing how deep ecologists' views would change upon becoming more rational.

The suffering is bad, but there are other values to consider here, that the scenario includes in far greater quantities.

We have different intuitions about how bad suffering is. My pain:pleasure exchange rate is higher than that of most people, and this means I think the expected suffering that would result from a Singularity isn't worth the potential for lots of happiness.