We should certainly try to be ready. If we're going to need to make further schema updates for IPv6 anyway, I'd rather we try to fix rc_ip while we're at it.
Aaron's provided some additional info for needed MediaWiki-related changes, which I've copied here:
https://www.mediawiki.org/wiki/IPv6_support_roadmap
I've created a tracking bug here for blocking issues:
https://bugzilla.wikimedia.org/show_bug.cgi?id=35540
We'll continue to sync up on this internally both from an ops and development standpoint, but anyone who wants to help move this forward, please do.