I guess I'm looking at the survivability. if all of a sudden something happened where majority of these ASICS got shut down (within 2-3 days, 80% of ASICs are taken offline) for whatever reason. What is going to happen? will the 20% of the ASICs left from rest of the world, going to handle the hashrate?
What's going to happen is that finding blocks is going to slow down for a while, and then go back to normal once difficulty adjusts to the lower hashrate.
with only 20% of the hashrate it will take hours to find any block and as a result the difficulty adjustment target which is happening every 2 weeks or 2016 blocks will take a lot more time to be reached. in other words we may not see any difficulty adjustment for months.
keep in mind that because sudden loss of 80% of the hashrate is an impossible thing, this scenario is also considered an unlikely one and as a result if it happens, it will require special actions such as a fork at that time to solve the difficulty problem.