The conversation in the two posts you replied to isn't about whether you always want to be on the bleeding edge all the time, it's about whether it makes sense to have a centralized repository that contains the latest version on some supported channel, which isn't necessarily the same thing as the latest -nightly. I take the position that it is; that shipping a (potentially) different version of a library with every application is a bad approach which is often less secure and harder to maintain.
There is a new version of the Rust library. In theory, either anything that supports it should be updated selectively (i.e. Firefox) or all consumers should be updated in lockstep. Yet in practice the maintener decided that neither option was feasible so nothing was updated at all. What went wrong here?
This reasoning assumes that future versions of software are always better. This is certainly not the case. I would like that a working program does not spontaneusly break because a third party "upgrades", thus introducing a new bug. I am willing to give up anything else to be assured that working programs continue to work no matter what.