There is another hope in this regard, when the mining will not reap much profit, all the big miners will leave the scene and then home mining will be possible if anyone is willing to support mining and as a reward you will get the mining fees.
Then Bitcoin will be a sitting duck for anyone who wants to launch an attack.
Dunno how mining will work itself out but it needs to be as muscular as possible if BTC takes a step up in use and visibility. There'll be an ever increasing number of entities with an incentive to mess with it.
Arguably, the difficulty is being driven unnecessarily fast because of miner speculation on the existing subsidy, and some eventual decline in the hash rate would be fine and expected. Whether it's an orderly decline -- as opposed to a downward spiraling crash -- is what matters.
The problem is, we have no idea how much fee pressure is enough to strike a balance between sustainable mining rewards and the diminishing returns from mining speculation. Segwit's 4MB limit may already be pushing the upper bounds since we can't just rely on mass adoption. We need to make the system sustainable with or without an exponential increase in user base.