UTF-8 by default?

Hello!

I've just joined this list, so I apologize if this has been discussed before.

Today in #freebsd on FreeNode, I've asked whether there was any
particular reason why UTF-8 wasn't the default in FreeBSD yet.
What followed was a small discussion regarding this, and it seems that
there's a good number of people who'd like to see that done. One
mentioned that 11 would be the perfect opportunity to make this switch
(although I understand it might be too late by now --- maybe 12.0?).

It would definitely help internationalization (I was half-considering
posting this to freebsd-i18n list instead, but then I figured this one
would be more appropriate), and I can't see *that* much of a reason
not to use it.

So, without further ado:
1) What are the reasons that UTF-8 isn't the default yet?
2) Would it be possible to make this the default in 11.0? What about 12.0?
3) Assuming an effort is started towards making UTF-8 the default,
what changes would be required?