At current ratio, the ATI Radeon HD 4890 draws 190W from the wall socket, hence the Maximum current draw of 225W [75W from PCIe slot, 2x6-pin for 150W]. But this 2x6-pin is not final, since reference boards feature room for a 300W TDP configuration [75W from PCIe, 8+6-pin for 150+75W], for the ultra-overclocking boards.
However, our sources in Taiwan claim that the ultra-overclocked board e.g. SuperRV790 isn't exactly what they are interested in. AMD GPG [Graphics Products Group, e.g. division F.K.A. ATI] recognized the need for even more powerful part, and gave the thumbs up to partners that want to do the 4890X2. In a YouTube interview for PC Games Hardware, Sasa Marinkovic [Product Manager for Consumer platforms: CPU, GPU, Chipsets] practically confirmed the X2 part. You can fast forward to six minutes into the interview for the "we're going flat out to capture the crown" statement.
Current king of the hill is GeForce GTX 295, dual-GT200b based card. Our sources claimed that they are ready with their own 4890X2 designs - power issues, in worst case can be addressed with two 8-pin connectors. If this truly comes to life, a 4890X2 would be the most power-hungry card on the market, with a potential to eat 375W [75W from PCIe slot, 2x8-pin for 300W].
When we asked about the fact that there are no dual 8-pin parts out there, explanation was simple: almost every decent power supply on the market has two 8-pin and two 6-pin connectors for Crossfire and SLI configurations, most of 700W+ ones come with three 8-pin and three 6-pin ones for 3-Way SLI. There is one ATI partner that actually plans such a design and wants to do dual-1GHz GPU clock, partnered with 2GB and 4GB of GDDR5 memory. We are going to leave to speculation what might be the identity of that partner, but know that we managed to see some very interesting engineering drawings.
You can expect 8+6-pin Radeon HD4890X2 2GB and 8+8-pin overclocked Radeon HD4890X2 2GB and 4GB parts. Unless PM's of respective companies don't get into frenzy mode and stop the parts. That would not be wise, guys.
It can never get boring in the world of graphics, always have that in mind. ;-)