And that's not all. With the introduction of Touch ID, Apple has shifted to 6 digit passcodes as the standard. The authors note that their method would not work so well, even if they had infinite time:

"Given six attempts per each rewrite this method would require at most 1667 rewrites to find a 4-digit passcode. For a 6-digit passcode it would require over 160 thousand rewrites and will very likely damage the Flash memory storage."

If you want to decrypt the modern iPhone you'd probably have to try to poke inside of the secure enclave with an SEM or something. And then you're getting into the realm of hardware defenses against this kind of intrusion, like physical self-destruction when probed.. not sure if Apple's doing anything there but it's crazy stuff.

[1] https://www.apple.com/business/docs/iOS_Security_Guide.pdf (page 12)