The only miners that might shutdown their equipment is when all of a sudden they look at their pool stats and they are making half somehow. These are the novice miners which only represent a small percentage of the overall network.
All the miners will look at their earning and they will make zero!
The reward having will happen Monday night, the difficulty adjustments will only happen one week after.
So, everybody will make at least for one week half of what they were making.
People assumed this back in 2016 and they were expecting the network to halve in hashrate and the blocks to be 20 minute long. However look what happened instead. From the hashrate charts it looks like it remained the same after the halving.
You're ignoring one thing, the advance in efficiency.
Till the middle of 2016 the best gear available was something like the s7, then bitmain launched the s9.
4.7 Th, 1210 W, 0.25 W/GH
14Th , 1375 W , 0.09 W/GH
That's an increase in hash rate for the same power consumption of 2.5 times.
The difficult should retarget in 6 days after the halving anyways so even if 20% of miners leave the difficult will adjust fairly quickly and we will get 20 minute block times back.
I doubt that part!