Reply to comment:

Emile Aben
We do have IPv6 traffic level graphs available for one IXP (DECIX), these are available from the overview IXP traffic stats page, labeled 'decixv6fra-de' ( the link is: http://albatross.ripe.net/demo-area/ixp-olympics/ , also linked in the article above). We didn't do any specific analysis related to IPv6. If you find interesting traffic patterns in there, let us know!