It is technically supported in v0.12.0 (current mainnet release) -- however, this is being removed in version 0.12.1x as a temporary workaround to solve Proof-of-Service issues. Not all nodes are able to connect to IPv6 and those MN's are unable to service IPv4 nodes/clients. That said, there will be a transition plan to enable IPv6 in the future, though it might not be IPv6-only.And now?