See the current ISO status, and the new ISO Standard.
As users of a source-based distribution, we have the unique opportunity to shape the future behavior of a package because we compile it before we use it.
In many cases it won't be necessary, but if your packages depend on something like C 11, then you might run into problems - see e.g.
the Gentoo news about ABI change in GCC 4.7 or GCC bugzilla.
First off, let me say in response that as a user of a source based distribution, I firmly believe what connects the dots are all the things you've asked for in your bounty request.
Someone can be a great coder, but have crappy care for software.
TL; DR I have a different take on this as a Gentoo user.