The problem is in this statement:
Logically, the hash rate only needs to be sufficiently high to process all of the transactions requested.
The hash rate is
technically independent of transaction volume. If the hash rate were to drop to 1Mhash/s right now, then the target difficulty would soon follow. Bitcoin is set up to produce a new block every 10 minutes, regardless of hash rate. Thus block space remains constant.
Yes, understood. However, this is just asserting that if the hash rate falls, the difficulty will adjust. The problem isn't the difficult level, but the falling hash rate (reducing the barrier against a network attack).
Now, given that block space is a finite resource, there will be competition. More competition (more transactions) will drive up fees, which will make mining more profitable, thus increasing the hash rate as more miners join in to get that profit. Conversely, less transactions means less competition, less fees, less mining, reduced hash rate.
Sure, I'm fine with this too. I asserted that 'if the transaction rate becomes stable', then so will the competition for block space. In turn, this implies a stable hash rate (fluctuations considered, ofc).
Now, when hardware becomes cheaper, mining becomes more profitable. Thus more miners join in to get that profit. Any guesses what that results in?
Bottom line: as long as there is competition for block space, this entire thread is moot.
I asserted that 'mining ceases to be profitable' as a boundary condition. I'm not convinced that
miners drive the price of Bitcoin; It's the
people who value Bitcoin that dictate the price. If it becomes too expensive to mine at the market rate, mining will not be done. Therefore, I'm not convinced that miners will
necessarily step up to increase the hash rate.
To conclude, I am still unconvinced that this thread is moot. The hash rate needs to increase proportionately to Moore's Law and I'm not certain this will happen automatically (without some relatively minor alternations).
I'm happy to be proved wrong though, if you think I'm still missing something.