AMD representatives told us that with MSI K9A2 Platinum you should be able to plug four R680 cards inside. This would mean that you would have eight GPUs, but at this time there is no driver to support this feature.
CrossfireX can do two, three or four cards, not more than that, but we've see that four-way Radeon 3850 is actually doing alternate frame rendering with eight frames, and this clearly indicates that if you can do four, it should be possible to do eight.
It would be a great show off system and it is nice to know that four cards will work with two GPUs each. It is simple math: eight is far better than four, however we would not expect great performance. But, at least it would look cool.
It is pretty much up to Ben and Terry to make us a driver. How about it, guys?