You can't be absolutely sure what BIOS version the MB will come with, no. Places like Newegg and Amazon have a big turnover, so chances are pretty good that the MB will have the latest BIOS. But that's just speculation. Since the A10-7850K is the most recent APU, there is a small chance that the MB's in stock won't recognize it.
You can't flash a BIOS without a processor installed. So, I see three choices. Take a chance and buy the MB and hope it has the latest BIOS, Contact the retailer with your concern, or Pick up an inexpensive Athlon X2 340 ( http://www.newegg.com/Product/Product.aspx?Item=N82E16819113330
) and use it to flash the BIOS if needed... then sell the Athlon. Of course, with the Athlon, you will need a discrete gfx card to get a display since the Athlon has a disabled on-die GPU.