They are very different games, and while it's true we've seen quite a few console-related threads lately, I don't think it's going to last that much. It's probably going to be more of a novelty thing.
The amount of console-related threads has already decreased over the past week or so, and with Blizzcon and the RoS coming closer, I think we'll see a heavy sway towards the PC version even more. As long as it's not generating 1-2 pages of new discussions on a daily basis, I don't think a subforum is really necessary.
That's how I see that matter at least.
But we will keep an eye out for that, if it starts clumping the forums, we'll do something about it
It's not really because it's making the general forum messy - not at all.
My concern is that people discuss about wrong context. Whenever people discuss game play related questions (see the recent "team" thread) it makes a huge difference whether you're talking console or PC. Same with "endgame difficulty" or "gear progression" and ultimately "economy". The OP might forget to add console tag or people like me tend to overlook these tags and answer based on assuming this is about PC.
It's like hardcore - in my opinion, it should have a sub-forum just because it's almost like a different game mode, with entirely different mechanics and context, such that intermingling these discussions can lead to serious miscommunication. Plus, wouldn't it be nice to be able to view all console-related threads in one go...
That's how I see the matter ;-)
Pick your side! (P.S.: Free cake on my side.) (P.P.S.: The cake is a lie.)
I don't see the reason for not having a console sub-forum, though, to be honest. It's not like general discussion would be dead without it or benefit from having mixed threads.