You can plug four to eight Lasso external R600 cards and make them render all together. We found a few details about the external R600 Lasso system. You can connect them via external PCIe. R600 lasso works with uses external PCIe and my old folk on the inq wrote about it here.
ATI is also thinking about separate housing for more R600 cards to render in Crossfire. We heard the number of four to eight cards is possible.
Our sources confirm that you will be able to connect the cards via External PCIe. The part we don’t understand is where you plug such a card. The closest to a reasonable explanation Is Nvidia's Quadro Plex box with bunch of cards. You can take a look Nvidia's PDF here.
You still end up with an internal PCIe interface card that will connect the Lasso cards. Lasso interface card should let you plug four to eight R600 cards in its own housing, just as Nvidia did with Quadro Plex box but this is only for the rendering market and it is very expensive.