The title says it all, but just to clarify. There is a treasure trove of information in the old forum. So will it be up indefinitely in read only mode or end of life time is already counting down?
Edit:
Actually, I would love the ability to download all of my post from the old forum. Can you give it to me in XML format? That would be super sek-C.
WoW has been on the new forum format for a couple of years now, I think, and it’s old forum archives are still accessible:
Of course, that doesn’t mean that any of the old archives will be there indefinitely.
Well, actually, a large chunk of WoW’s archives are gone.
See, they used to have several different forums, called the “Role” forums - Damage Dealing, Healing, Tanking.
When they upgraded the forums the first time - to the read-only archive you linked to - they erased those forums.
There were a metric ton of posts there, especially in the Damage Dealing forum. All of them are gone now… you can still see links to them in the histories of posters (such as me, when I peruse my history), but you can’t access them.
Something similar happened to the Diablo 3 Europe French language forums I monitor… when Blizzard switched us all to the new forums, they “wiped out” all the class forums… along with the various build guides !! Or so we thought.
Took some time, but I eventually figured out that all they did was “mask” the class sub-forums home page… the one with the listing of all the conversations. The conversations themselves are still available, but the listing is not. I now know that Blizzard can see those listings.
I have the old URL for the 7 classes sub-forums… but they don’t work and I get directed to the main forum page when I try to access them. One of the player who did the guides for Monk did come in the conversation, and I showed him how to use his Post History to try and recuperate the guides… even found 3 conversations that looked promising. I don’t know who the other guide authors are and, unless they show up in that conversation, I’m not going to be able to do much.
I don’t know why Blizzard did that… I checked the other languages on the old forums, and they still have their class sub-forums… 
I have now reached out to one of the Heartstone Europe French language moderator (don’t know why she was assigned to our group – availability I suppose) to try to make those listings visible to us again… In her e-mail to me, she did mention that “… Les anciens forums vont disparaître d’ici peu,” (the old forums will disappear soon) but she did not elaborate on the time frame.
I’m opened to suggestions…
As someone with over 5000 posts in the old forum, this is important news for me.
I just hope there is a warning or something when the old forums will be removed so I can go back through some of them for nostalgia’s sake (mostly the brawling forum).