In the highly unlikely scenario all miners cooperated and...
1) All miners are taken off the network at the next difficulty re-target.
2) In the following two weeks difficulty is re-targeted to zero.
3) All miners then come online and exploit the difficulty.
4) Nobody attempts a 51% attack during the process.
0. Highly unlikely.
1. For all intents and purposes, impossible, not even a majority.
2. For all intents and purposes, because of 1, impossible.
3. Won't happen, because 2 won't happen.
4. With such a low difficulty, someone will attempt this.
I just woke up and had this thought in my head.
Go back to sleep.
In order for 1 to happen, you have to forcefully destroy those miners, or forcefully disconnect them from the internet. We will have other problems when that happens.