No, they have not been leaked yet.Your going to have to wait till it's closer to the day Win 7 hits the stores.
I may add that since we can activate with Vista certificates, there won't probably be a need for ASUS cert (if the cert matches the RSDT/pub/marker data). What's missing is the ASUS SLIC 2.1. Nowhere to be found (constantly searching all new BIOS updates on Asus FTP site).
I dont think posted BIOS updates would include new SLICs on their websites. When you download a BIOS update (direct from manufacture), the area of the SLIC does not get updated. The SLICS are only included in new factory shipped PCs. More than likely you'll have to wait until Asus notebooks ships with 7 on it.
It all depends on the switches used when flashing the BIOS. But I agree with you - according to the latest documents from MS big vendors shouldn't update the SLIC table with bios updates. Anyway - I'm still checking the bioses - just for fun and to make sure we don't overlook anything