Here is the comment you linked:

> Ian's proposal demands too much. We cannot possibly develop all the features at-once, it will exist in an unfinished state for many months.

> In the meantime, the unfinished project cannot be called official Go language until done because that will risk fragmenting the ecosystem.

> So the question is how to plan this.

> Also a huge part of the project would be developing the reference corpus. developing the actual generic collections, algorithms and other things in such a way we all agree on that they are idiomatic, while using the new go 2.0 features

The author of this comment is not a member of the core team, as far as I know, and the comment doesn't suggest the proposal was rejected.