Look, this is just my opinion, based on my limited experience, but I don't think this is a huge priority...
SERIOUSLY limited experience.
See, there are some small organization (like the US government) that demand IPv6 capability. Part of the long/mid term policy. No IpV6 - hard time selling there. That simple.
Even my small shop starts moving into IpV6 for our internal network, completely. We are not there yet (even MS has some products not supporting IpV6 yet), but it is one point on the list. Why bother with the hard to maintain IpV4 in emergency cases (either hardcode all network settings - which is hard to maintain - or DHCP may not trigger if a server starts before the dhcp server) when IpV6 handles dynamic address reallocations (addresses assigned when the network router boots up) perfectly well

Among other things.
IpV6 is absolutely NOT ONLY about the hugh address space. It is also about ease of management.
Nice to hear v5.5 will add it.