Well, considering the slot is spec'd for 150 watts and a 1x8 (2x4) PCIE plug is spec'd for 150 watts. Someone at one or both of the major IHV's is expecting to push 150-300 watts at least. Designs don't generally change so drastically without some expectations of it's being used at some point in the future.
Is it going to be the R700 2, 4, 8, 2348795234 core card? Or maybe some monolithic Nvidia 1 million billion quadrillion transistor core? Who knows. I just know at some point in the next year or two I expect one or both of them to push out a high end card at some ungodly price pushing 300 watts or possibly even more.
Is it going to be a huge seller? Does it matter? In the quest for the ultimate high benchmarks on web reviews "sell ability" doesn't seem to matter one whit. All you need to do is look at the 7800 GTX 512. Reviews were still coming out based on that card even when you could no longer buy it. And proclaiming Nvidia the fastest in the land because of it. Even though...you know, you couldn't buy it except on Ebay.
So yeah, I fully expect ATI or Nvidia to release some monsterously large and impractical card for the sole purpose of proclaiming FPS godhood on review websites. Although with ATI's aparent focus on the mainstream and mainstream performance market, I'm not sure Nvidia will have to do much to claim the fastest ever e-penis crown.
Regards,
SB