Few more informations about this issue :)

I tried to contact with my isp, and kindly they help me figure out what is going on, even when im not using their CPE (they support you only when using the provided cpe from them). In resume and with my bad english i'll try to report back here what they told me (translation in english --- bad actually :p)

"As it seems, the CPE (td-w8970), trying to get ipv6 address for wan and lan at the same time with DHCPv6 and that is not normal, because he should use SLAAC for the WAN part and not DHCPv6 for both of them. Actually the CPE (td-w8970) asking for IA-PD and IA-NA with DHCPv6, but the right is only IA-PD. The results from this behavior is the DHCPv6 not returning address in IA-NA, so the CPE (td-w8970) rejecting and the normal prefix too which he had get with IA-PD for the delegation in LAN. That behavior perhaps explains that you are seeing, the CPE seems not getting ipv6 address in WAN and LAN.

In resume, the CPE (td-w8970) as it seems getting normally ipv6 address in WAN with SLAAC (my comment not from isp: td-w8970 does not have SLAAC, i cannot seeing it anywhere in web gui), but for some strange reason he asking (the cpe --- td-w8970) ipv6 address for WAN with DHCPv6 in the same time with the ipv6 prefix for the delegation in LAN. The DHCPv6 server returning normally one ipv6 prefix for the delegation, but returnig "NOADDRS-AVAIL" for the WAN, with the results CPE rejecting and the LAN prefix too. Perhaps contacting with manufacter company of your CPE will resolve the questions and the issues"

Another post from them for the same issue:

"According from the logs of DHCPv6 server, for that particular CPE (TD-W8970), the prefix delegation (IA-PD) working normally as should, but the problem is at the same time requesting ipv6 address with IA-NA, which is something not supported with current setup of forthnet (isp). In theory, if will be added the manual option for SLAAC (for WAN?) as it looks from the beta firmware of TD-W8980 (commend from me not isp ---> i have show them the current thread here, and the links from the same issue as the guy from australia and the beta firmware), maybe , just guessing, the DHCPv6 IA_NA request which cause the problem will be disabled, and the issue will be not anymore there..."

So, as i understand, the problem is DHCPv6 IA_NA and the lack of SLAAC option for the WAN "part" of the story... TD-W8970 does not have SLAAC anywhere in settings... That is my findings for that issue until now. I dont know if a beta or official new firmware can solve it, but i just report you what i know... It is same, a full featured CPE like TD-W8970, with very good performance and quallity in all areas, having problems with ipv6, in fact the ipv6 is totally broken, unusable totally...:(

They have published beta firmware to add this feature, you can go to the software update Corner of the forum to find the downloading link.

http://forum.tp-link.com/showthread.php?72551-Added-the-IPv6-stateless-configuration-feature&region=china

Thank you :)

I contact with them with email, before their post there and they have send me with email the same firmware. The problem with ipv6, has been solved with this test/beta firmware :)