In my opinion, if it were easily possible so, it would be best to have only one
central repository including the documentation, e. g. something like
doc.ruby-lang.org or a sub-page like that.
As it is right now, when I search for documentation (via google usually),
and don't specify anything else, I also find old ruby versions first,
which is not a huge problem but a bit annoying. (I understand that we here
have no control over what Google does and how it caches, but I still think
it would be best to have all documentation in ruby bundled in one page;
I actually even think that gems should be available under
gems.ruby-lang.org, but again, I understand that unification is not trivial
due to disparate servers + content on these servers).