When you say "details very much might have changed between then and now", are there any news on bringing in the float128 type? I mean, do you happen to know whether there is any reasonable chance of having it in Rust at all?
Nobody since then has championed it, so there's been no progress. Because of that, I'm not aware of how much effort it would be to add; the compiler has changed a lot since those days. That might make it easier or harder.