According to Ars Technica,
Jonathan Zdziarski, a leading independent Apple iOS security researcher and forensics expert, has a theory about the FBI's newly discovered potential route into the iPhone 5C used by San Bernardino shooter Syed Farook. In a blog post, Zdziarski wrote that the technique the FBI is planning to use to get around having to compel Apple to help bypass the phone's security is likely a method called NAND mirroring—a hardware-based approach that, while effective, is far from the "golden key" software the FBI had sought.
This has been repeated in a number of other news outlets.
From what it sounds like, it won't be unlike what @user9806 posited a month ago.
However, as @Xander notes:
Yes, it is possible. However, that runs the risk of destroying the device without getting the data off first, which is undesirable.
Which leads me to wonder, what processes are involved in this technique? What exactly does "NAND mirroring" involve that prevents the chip from being destroyed?