As far as I know there aren't any well known (or even up and coming) certifications specifically geared towards IPv6...yet. I suspect they will start coming once consulting on IPv6 transitions becomes a thing...and I'm pretty sure it will. Some day CIOs will wake up and decide they want IPv6 because they read about it somewhere, or their buddy CIO is doing it, or their competitor is doing it, or a supplier is requiring it, or a customer is requiring it, or any one of a million other reasons.
When that day comes there will be demand for a good number of IPv6 transition consultants because:
1) Most IT people are too busy doing their job as it is to learn IPv6, especially IPv6 transition strategies. It's not something you can learn in a couple of afternoon workshops.
2) IPv6, especially transition strategies, is complicated enough and foreign enough that it can be confusing at first to get your head around it.
3) If you do it wrong you can cause lots of problems
4) The transition and planning part, which is the trickiest part, is a one-time thing so it will likely make sense to bring in a consultant.
The demand for consultants with a fairly new technology (well, sort of new, new to most people anyway), meaning that experience is hard to come by, will likely encourage some sort of IPv6 certification movement to substitute for experience in verifying skills.
All that said...take another look at the CCNA. You're likely to need this if you want to be taken seriously in networking anyway and Cisco has consistently been adding more and more IPv6 to it in each of the last several revisions.