I understand why initially the WotLK forums were put into place. During the beta it created a location to house things about Wrath, and keep TBC forums separated.
However, now that Wrath has been live for a few months and there's not really any reason to have a separate Wrath and "Regular" set of forums.
I have no idea how difficult this would be to merge them, but the Wrath ones should go away (or the regular ones) and just have 1 set of classes forums, PVP, general, etc...
When I browse the forums I generally ignore the older forums and wonder how many people post on them expecting a response.
Just my 2 copper!