Earlier today, AMD released Catalyst 8.4. In the release note they did not mention any improvement of the proformance but lots of the minor issue corrections. Anyway the driver actually contains supports for HD3850 X2.

“ATI Radeon HD 3850 X2″ = ati2mtag_RV630, PCI\VEN_1002&DEV_9513

So it seems the card is coming soon?

Driver download here

release note here