This message was posted on behalf of Intel Corporation
Thank you for contacting Intel Support,
I understand that you want information about a BIOS update for 4th Generation processors in regards the "Spectre" situation.
In regards this, Along with other companies whose platforms are impacted, Intel has worked with operating system vendors, equipment manufacturers, and other ecosystem partners to develop software and firmware updates that can protect computers from these methods. It is important to apply mentioned updates as soon as they are available.
For details on how to protect your system please refer to this site for more information
This is all the information he handle at the moment, I apologize for any inconvenience.
Translation: Intel has released microcode updates to OS vendors, board manufacturers, etc. It is up to them to deliver updates that incorporate these microcode updates. Bottom line, you need to ask (in your case) Asus regarding when they will release a BIOS update for this board that incorporates the updated microcode.