It seems odd that so few understand the dynamics of exponential growth on even a basic level.
The difficulty level cannot continue to double every few months forever. You can start with the laws of thermodynamics, and realize that in just a 5 more years of doubling it would utilize the entire energy output of the sun for hashing with even quantum computing. It had to stop increasing at that rate, and it did.
Additionally, from a commercial standpoint, many endeavors were built with a specific BTC/$ value. If you built out a large mining operation based upon $500/btc you are bleeding and will probably shut down in the near future. However, if you bought a miner for your home and are running it, you are dancing in the street. You can watch the $/btc rate jump from $100 to $1000 and back to $100 and afford to keep hashing. You can hold pretty much forever, unlike an ongoing major mining concern. And when the difficulty steadfastly refuses to increase, the life of your gear just got extended, and so does your ROI.
My crystal ball predicts a movement towards decentralization of mining. Larger mines find it difficult of survive large $/btc swings for extended periods.
I disagree with most everything you said. Yes, growth of the network had to slow eventually. But home miners are still incredibly disadvantaged compared to large scale mining operations especially the ones who design and build their own miners and enjoy extremely low electricity rates.
Hobbyist home miners may be able to continue to mine at a loss if they have lots of excess income and/or super cheap electricity. But a more serious miner with a significant investment in a home mining operation can't continue to profit with average electricity costs. They'll soon face serious losses.
For example, I don't have much excess income at the moment and need to sell BTC every month to pay ridiculously high electricity bills. I'm lucky if I break even and my electricity costs are only .11/kWh. I certainly won't continue mining when I'm in the negative. And I'm definitely not the only person who is in this situation. I can afford to keep a couple of my most efficient machines running but the vast majority of my gear will get tossed in the bin when that day soon arrives.