2. Bitmain flipping the kill switch.
Now the first one is unlikely because such a step will only hurt their investments by denting bitcoin's reputation. Bitmain flipping the kill switch and outright attacking the network as a last resort to prop up BCash is the most likely scenario.
What do you mean by a "kill switch"?
Do you think that Bitmain has some kind of backdoor in their ASICs which would allow them to seriously damage the equipment? Also, Bitmain controls a lot of hashpower, they could slow down the whole network if they turned off their ASICs right after the difficulty adjustment.
I don't think that Bitmain has a backdoor, I know they do. While it doesn't damage equipment, it does prevent them from mining. This backdoor is in almost all S9s (probably only the first few batches were safe). While you can mitigate it with a hosts file change, I doubt many miners know of this.
It's called AntBleed.Thanks for the insight, seems very interesting to me. Do you think this might have an effect on POW coins with low hashrate to switch to something like proof of stake or other alternatives to ensure security in their network?
Perhaps it could, but I don't think it would be worth it to attack. There's an extremely high cost for a rental, just to mine some coins that you plan on destroying the value at. POS has it's own problems.