I'm using 2.3.2-2 from the EPEL repository in CentOS 6. From what I can tell, learn-address does work with IPv6 in this version.
(note: In my config, I use both server and server-ipv6 for dual-stack inside the tunnel.)
If we setup a learn-address script:
#!/bin/bash
echo $1 $2 $3
When a client connects, in the log I get
add 1.2.3.4 CLIENTCN
add 2001:1:2:3::4 CLIENTCN
So you will have to handle them separately if you're running dual-stack
