No, you need a supported CPU installed before you can flash the BIOS by any method as without this the board won't fire up. I know, I've had this happen to me on several occasions and I now have a couple of "low end" CPU's just for this purpose.
The big problem for all motherboard manufacturers was that initially AMD planned to release the FX processors in March/April. Motherboard makers released these boards but, due to the problems at AMD the processors were delayed and also the microcode needed for them was updated. The upshot of this is, that there are a lot of "AM3+" ready boards on retailer's shelves, that sadly don't work out of the box with the new CPU's and need a BIOS update before they do.