The only way this mining system works is if the price of BTC rises. It's like a ponzi.
Difficulty just went down for the first time in 2 years which shows mining is tapped out. If the price of BTC goes up, the hashrate will increase and everything works. BUT if the price of BTC falls, here's what happens.
Say it falls to $100 over the next year and a half. The hashrate will drop to 30% of what it is now. THEN ADD IN THE REWARD HALVE AT THAT TIME, the hashrate will drop another 50% on top of that. So we will be sitting at 15% hashrate of what we are at now which would seem fine and dandy because the network worked when it was only 15% of the size it is now. The problem is back then, there wasn't an available supply of power to attack the network. The miners didn't exist yet.
If we went to 15% now, there are loads of farms who had shutdown miners who could flip a switch and turn them back on and attack the network with ease. Why would they do this? Maybe they invest heavily in the "next" coin and make more money on that when they crush BTC and everybody moves to something else. They could make way more money doing that then having a warehouse full of worthless doorstops.
You're saying miners will drop out because they can't compete, but
they'll somehow be able to jump in later (when other miners drop out)
and successfully attack the network? Yeah right. Even if they
turn back on, they will make more money mining than attacking.
Attacking Bitcoin so another coin can rise? Never gonna happen.
This doesn't make sense either. Miners are ALWAYS dumping
coins on the market. So what?