I dont think its going to happend anytime soon and definetly not with stock cooler as this card is going to be extremly power hungry and hot even without overclocking. I did myself ordered 4870x2 yesterday and i am planning to put some nice water cooling on it, probably from www.aquacomputer.de once they finish water block for this beuty. Personaly i think thy are making one of the best water blocks on world
I don't think you are going to see aftermarket versions of the 4870x2 for a long time. The reason for that is that DDR5 is in such short supply.
Right now there are a lot of over clocked HD4850s with after market coolers but there are no HD4870s with aftermarket coolers. I don't think ATI is going to allow aftermarket versions of the 4870 and 4870x2 until DDR5 supplies increase. And once they do increase I think the 4870 will get the aftermarket upgrades first before the 4870x2 ever sees it.
Never buy a stock OCed gpu. If anything grab yourself an Asus. You can OC it with a click of a button or through the utility. You also gain great temp and vol monitering options along with sweet fan controls.